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Allen KamravaMD · MBA · FACS · FASCRS

Is a pilonidal cyst dangerous?

In people with a pilonidal cyst or sinus (including during pregnancy), what is the risk of serious complications such as abscess formation, systemic infection, or (rarely) malignant transformation if the cyst is left untreated or recurs?

How people search for this, in their own words

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Evidence review in plain language · compiled 2026-10-29 · checked 2026-10-29 · next 2026-11-29 · automated review, how it works

What the evidence says

Bottom line

A pilonidal cyst is usually not dangerous, but it can become infected, and in rare cases long-standing disease can lead to serious infection or cancer.

Studies that followed people having pilonidal surgery found abscess (infection) is the most commonly reported complication, and recurrence happens in at least 1 in 10 people after excision. Cancer arising from a pilonidal sinus is rare — found in about 1 to 2 of every 1,000 surgical patients in the largest cohort — and almost always follows many years of chronic, recurring disease. No study in this review looked specifically at pilonidal cysts during pregnancy.

How well studied

Fairly well studied

Answered by 3 studies looking back at patients' records.

This question asks what a condition can lead to, not whether a treatment works, so there is no benefit-or-harm verdict. What can be shown is how well it has been studied.

answer it directly
15answer it directly
studies found
29studies found
randomised trials
0randomised trials
people studied
6,202people studied
years covered
2013–2026years covered

What the research shows

  • Abscess formation or acute infection

    Multiple studies describe abscess and infection as a common complication of pilonidal disease, sometimes requiring emergency incision and drainage.[1,2,3,4]

    Found in studies

  • Systemic sepsis or hospitalization

    Isolated case reports describe rare, severe spreading infection (a toxic shock-like illness, a spinal abscess) linked to a pilonidal abscess, but these are single cases and cannot show how often this happens.[1,2,3]

    Some evidence

  • Recurrence rate after conservative vs surgical management

    Recurrence was reported after both surgical excision (at least 10%) and non-operative treatment (higher if an abscess was present), but no study directly compared the two approaches head-to-head.[1,2]

    Too little evidence

  • Malignant transformation (e.g., squamous cell carcinoma) in chronic pilonidal sinus

    Cancer arising from a long-standing pilonidal sinus is rare — about 0.1% to 0.2% across case-report-based estimates, and 2 of 1,505 patients (0.13%) in the largest surgical cohort — occurring mostly in older patients after years of disease.[1,2,3,4,5,6,7,8]

    Some evidence

  • Pregnancy-specific complication rates

    No study in this review looked specifically at pilonidal cysts during pregnancy.

    Not studied

  • Need for emergency surgical intervention

    A review reported that emergency incision and drainage for pilonidal abscess is needed in more than 10,000 people a year in France, though this was not expressed as an individual risk percentage.[1]

    Some evidence

What the studies found

  • Most of the serious outcomes found in these studies — repeat abscess, recurrence, rare cancer — occurred in longstanding or repeatedly recurring disease, not in a cyst that had just appeared.[1,2,3]
  • The largest cohort that checked tissue removed during pilonidal surgery for cancer found it in only 2 of 1,505 patients (0.13%), both older men with disease present for years.[1]
  • When pilonidal sinus cancer does occur, catching it while it's still a localised, raised growth is linked to much better outcomes than when it's already ulcerated and spreading.[1]

Important limitations

  • Most of what's known about cancer risk and severe infection comes from single case reports, which by nature cannot estimate how common these outcomes actually are.[1,2,3,4,5,6,7,8,9]

What kind of studies

  • Case series21 · 72%
  • Retrospective6 · 21%
  • Narrative review1 · 3%
  • Prospective cohort1 · 3%

The key studies

  • Darnis et al. 2025

    Management of pilonidal sinus and recurrences in 2025

    Can cause abscess, infection, recurrence.Narrative reviewLow quality

    size not given2025

    The abstract states pilonidal sinus 'can develop into abscess or suppuration,' requiring emergency incision and drainage in over 10,000 patients a year in France; elective surgery is done to treat symptoms or 'avoid the risk of recurrent abscess'; after radical excision there is 'a risk of failure or recurrence for at least 10% of patients'; primary closure reduces healing time 'at the cost of more frequent infectious complications'; active smoking 'increase[s] the risk of postoperative complications and recurrence'; and failure to heal or recurrence after excision is 'associated with a clear deterioration in the quality of life.' No mention is made of malignant transformation.

    Who was studied
    People with a pilonidal sinus (cyst) in the cleft between the buttocks
    Main outcome
    Whether the pilonidal sinus leads to abscess/infection, recurrence, surgical complications, or other harms
    Quality
    This is a narrative review summarizing clinical experience and practice patterns rather than a systematic analysis of risk data, so its statements about dangers are expert description, not rigorously quantified evidence.
    Limitations
    The abstract is a general management review, not a study designed to quantify risks; it gives only one specific risk figure (recurrence at least 10%) and does not address malignant transformation, pregnancy-specific risks, or long-term outcomes with methodological detail.

    Taken word for word from the abstract

    • population Pilonidal sinus is a common pathology of the intergluteal cleft that can develop into abscess or suppuration.
    • primaryOutcome If suppuration and abscess develop, treatment is based either on medical treatment combining analgesics, local antiseptics and sometimes antibiotics, or on emergency incision and drainage in the operating room.
    • result This is performed in more than 10,000 patients per year in France.
    • result Outside of emergencies, elective surgery for pilonidal sinus is indicated to treat bothersome symptoms or to avoid the risk of recurrent abscess.
    • result This strategy carries a risk of failure or recurrence for at least 10% of patients.
    • result Primary closure after excision can reduce the time for healing and convalescence, but at the cost of more frequent infectious complications.
    • result The surgical indication must take into account the patient's risk factors, particularly active smoking, that increase the risk of postoperative complications and recurrence.
    • result They have the merit of avoiding difficult situations of failure to heal or recurrence after radical excision that are associated with a clear deterioration in the quality of life.
    • harm This strategy carries a risk of failure or recurrence for at least 10% of patients.

    J Visc Surg · PMID 39875233 · Read it on PubMed ↗

  • Kudaş et al. 2025

    Pathological Examination in Pilonidal Sinus Surgery: Evaluating Necessity and Cost-Effectiveness: A 10-Year Retrospective Analysis

    Cancer in cyst tissue is rare.RetrospectiveModerate quality

    1,505 people2 years

    Cancer was found in 2 of 1505 patients (0.13%), both older men with long-standing disease; risk was higher with age over 40 and disease lasting more than 3 years

    Who was studied
    people who had surgery to remove a pilonidal sinus/cyst over a 10-year period
    Main outcome
    finding of cancer (squamous cell carcinoma) in the removed pilonidal tissue
    Quality
    Large retrospective series from one period gives a reasonable incidence estimate, but it is a single-center chart review without a comparison group and excluded patients with missing data.
    Limitations
    Retrospective design, missing histopathological data led to exclusions with no imputation, and only two malignant cases limit how precise the risk-factor estimates can be.

    Taken word for word from the abstract

    • population A retrospective analysis was conducted on 1505 patients who underwent surgical excision of PSD between January 1, 2014, and December 31, 2023.
    • primaryOutcome All specimens underwent histopathological examination to detect malignancies.
    • result Two cases (0.13%) of SCC were identified, both in males aged 50 and 58 years without a history of Crohn's disease, HIV, prior radiation, or other cancers.
    • result Significant risk factors for malignancy included age over 40 years (OR 3.2, 95% CI 1.1-9.5) and disease duration over 3 years (OR 2.8, 95% CI 1.0-7.6).
    • n A retrospective analysis was conducted on 1505 patients
    • followUp with both patients being disease-free at the 2-year follow-up.

    Am Surg · PMID 39544170 · Read it on PubMed ↗

  • Montebello et al. 2024

    Parathyroid Hormone Related Protein Mediated Hypercalcaemia Due to Metastatic Squamous Cell Carcinoma Originating from Pilonidal Disease: A Case Report

    Rare case: fatal cancer misdiagnosed as cystCase seriesVery low quality

    1 peoplewithin a year of diagnosis

    The lesion was not a simple pilonidal abscess but turned out to be stage IVb squamous cell carcinoma that had spread to lymph nodes and other tissues, caused severe hormone-related high calcium levels, could not be cured, and the man died within a year

    Who was studied
    A man with a long-standing pilonidal lesion originally thought to be a pilonidal abscess
    Main outcome
    Whether a pilonidal lesion could actually be a dangerous malignant disease
    Quality
    This is a single case report of one patient, so it cannot show how often this happens, only that it can happen.
    Limitations
    Only one patient is described, so no information on how common this risk is or in whom it occurs.

    Taken word for word from the abstract

    • population A 56-year-old male presented with a longstanding, gradually enlarging, painful, skin lesion over the natal cleft.
    • n A 56-year-old male presented
    • primaryOutcome This was initially thought to be a pilonidal abscess but, following multiple surgeries, he was diagnosed with Stage IVb squamous cell carcinoma of the natal cleft skin with bilateral inguinal lymph node metastases and subcutaneous metastatic deposits.
    • result Complete surgical cure was not possible.
    • result His course was complicated by severe humoral hypercalcaemia of malignancy (HHM) resistant to medical therapy.
    • result He died within a year of diagnosis.

    Br J Hosp Med (Lond) · PMID 39212563 · Read it on PubMed ↗

  • Salih et al. 2023

    Non-operative management of pilonidal sinus disease; classification and outcome

    Abscess raises recurrence risk after treatmentProspective cohortLow qualityRelated question

    3,529 people6 weeks

    having an abscess present was the strongest factor linked to recurrence after non-operative treatment; patients were grouped into three recurrence-risk classes based on combined risk factors

    Who was studied
    people with pilonidal sinus disease, mean age about 27, treated with a non-surgical injection method and followed for recurrence
    Main outcome
    recurrence of the pilonidal sinus after non-operative treatment, and which features predicted it
    Quality
    this was a single-arm cohort with no comparison group, short 6-week follow-up, and only about 29% of all patients treated were included in the analysis, which risks selection bias.
    Limitations
    no control/comparator group, short follow-up of only 6 weeks, and only a subset (3529 of 12123) of treated patients were analysed, so findings may not generalise; the study looks at recurrence after treatment rather than natural complications of an untreated cyst.

    Taken word for word from the abstract

    • population The mean age of the participants was 26.95 years, ranging from 14 to 55 years.
    • n of which only 3529 patients were included in this study
    • primaryOutcome The patients were seen at the clinic 6 weeks after the intervention to record data of recurrence.
    • result The most significant factor related to the recurrence was the presence of an abscess.
    • result After summation of all odd ratios, the percentage of each one from the total was calculated, and accordingly, the patients were divided into three classes.

    Int Wound J · PMID 37259676 · Read it on PubMed ↗

  • Safadi et al. 2023

    Pilonidal sinus disease carcinoma: Survival and recurrence analysis

    Rare cancer risk, but serious if it occursRetrospectiveLow qualityRelated question

    140 peopleup to 132 months

    Malignant transformation of a pilonidal sinus is rare but when it occurs it carries substantial risk: 3-year disease-specific survival was 61.7%, 5-year survival 59.8%, 10-year survival 53.2%, with worse survival in higher stage and poorly differentiated tumors; recurrence occurred in 46.6% of patients, mostly locally

    Who was studied
    People diagnosed with carcinoma arising from pilonidal sinus disease
    Main outcome
    Survival and recurrence after pilonidal sinus carcinoma develops
    Quality
    This is a retrospective pooling of published case reports collected over more than a century, so it cannot say how often malignant transformation happens among all pilonidal cases, only what happens once cancer has already developed.
    Limitations
    Retrospective collection of published cases worldwide, not a cohort of all pilonidal sinus patients, so the actual risk of transformation per patient with pilonidal disease cannot be calculated from this data; follow-up data were incomplete for some cases.

    Taken word for word from the abstract

    • population all reports of carcinoma developing on the background of PSD
    • n 140 cases of PSD carcinoma were published in 103 papers
    • primaryOutcome The study aims to determine the survival and recurrence rates of pilonidal sinus disease (PSD) carcinoma.
    • result The disease-specific survival rate was 61.7% for 3 years, 59.8% for 5 years, and 53.2% for 10 years.
    • result Recurrence occurred in 46.6% of the patients.
    • harm Pilonidal sinus carcinoma has a worse prognosis than primary cutaneous squamous cell carcinoma.

    J Surg Oncol · PMID 37195200 · Read it on PubMed ↗

  • Safadi et al. 2023

    Demographic overview of pilonidal sinus carcinoma: updated insights into the incidence

    Rare but real long-term cancer riskRetrospectiveLow quality

    140 people2023

    140 published cases of cancer arising from pilonidal sinus disease were found (plus 2 unreported German cases), occurring on average 20 years after diagnosis of the sinus, with a calculated worldwide incidence of about 0.17%, though the true rate is likely higher due to underreporting

    Who was studied
    People diagnosed with pilonidal sinus disease, mostly from published case reports worldwide and a survey of German hospitals and pathologists
    Main outcome
    Development of cancer (carcinoma) arising from long-standing pilonidal sinus disease
    Quality
    This is based on a survey and literature search collecting rare published case reports rather than a study following patients directly, so the true risk could be under- or over-estimated.
    Limitations
    Relies on published case reports and a questionnaire survey, subject to underreporting; incidence estimates varied widely (0.03% to 5.56%) across local studies.

    Taken word for word from the abstract

    • population questioning the surgeons and pathologists in Germany in addition to a literature research
    • primaryOutcome explore the demographic characteristics of this disease and to provide more precise information about its incidence
    • n we found 140 cases of pilonidal sinus carcinoma in 103 articles
    • result The worldwide calculated incidence equaled 0.17%.
    • result the interval between the diagnosis of the disease and the development of carcinoma was 20.1 ± 14.1 years
    • result Due to underreporting and other causes, the incidence of carcinoma emerging on the background of pilonidal sinus disease is higher than reported.

    Int J Colorectal Dis · PMID 36849571 · Read it on PubMed ↗

  • Oliveira et al. 2018

    Teenage boy with high fever and rash: what could we be missing?

    Caused severe, life-threatening infection in one case.Case seriesVery low quality

    1 people4 days

    the boy's pilonidal abscess was linked to a severe, life-threatening infection (low blood pressure unresponsive to standard treatment, needing intensive care) caused by toxin-producing bacteria in the abscess; he recovered after drainage and antibiotics

    Who was studied
    a teenage boy with a pilonidal abscess who became severely ill with fever and shock
    Main outcome
    severe complication arising from the pilonidal abscess (toxic shock-like illness)
    Quality
    this is a single patient's case report with no comparison group, so it cannot show how common or likely this severe complication is for people with pilonidal disease in general
    Limitations
    only one patient was described, there is no control group, and the report cannot estimate how often such a severe complication occurs

    Taken word for word from the abstract

    • population A 15-year-old boy was admitted to a local hospital with high fever, generalised rash and a mild sore throat.
    • n A 15-year-old boy was admitted to a local hospital
    • primaryOutcome This case report summarises a potential severe complication of the pilonidal disease.
    • result A sacrococcygeal pilonidal abscess was identified, requiring prompt surgical drainage.
    • result The microbiological culture of abscess material was positive for an enterotoxin-producing Staphylococcus aureus and Peptostreptococcus magnus
    • result develops a sustained low diastolic blood pressure (DBP), unresponsive to fluid volume expansion and cardiovascular support with dopamine
    • followUp He was free of symptoms after 4 days.

    BMJ Case Rep · PMID 29437816 · Read it on PubMed ↗

  • Iesalnieks et al. 2013

    Smoking increases the risk of pre- and postoperative complications in patients with pilonidal disease

    Smoking raises abscess and complication riskRetrospectiveLow qualityRelated question

    610 people1 year

    smokers had pilonidal abscess more often and more wound complications/recurrence than non-smokers

    Who was studied
    patients having surgery for pilonidal disease
    What they received
    being a smoker
    Compared with
    being a non-smoker
    Main outcome
    abscess formation, recurrence, and wound complications after pilonidal disease
    Quality
    This is a retrospective review of one surgical center's patients comparing smokers to non-smokers, not a study of the natural risk of pilonidal cysts in general, so it cannot reliably answer how dangerous the condition itself is.
    Limitations
    Retrospective design, and the comparison is between smokers and non-smokers rather than describing the general risks of having a pilonidal cyst.

    Taken word for word from the abstract

    • population Consecutive patients undergoing surgery for pilonidal disease between 1/2004 and 3/2012 were analyzed retrospectively.
    • intervention Smokers had developed a pilonidal abscess at least once during their disease significantly more often than non-smokers
    • comparator 48% vs. 26%, p = 0.00001
    • primaryOutcome The aim of the present study was to analyze the impact of smoking on the natural history and on treatment results.
    • result Smokers had developed a pilonidal abscess at least once during their disease significantly more often than non-smokers (48% vs. 26%, p = 0.00001).
    • result After the Karydakis procedure, smokers developed more wound complications than non-smokers (29% vs. 10%, p = 0.005).
    • n Six hundred and ten patients underwent 660 surgeries

    J Dtsch Dermatol Ges · PMID 23945165 · Read it on PubMed ↗

What actually helps, on this site

More about the condition:

All 29 studiesEvery study that answered the question, with its design, size and result.
The other 21 studiesEverything else the search returned, including anything retracted.

  • Garcia et al. 2026

    Patient characteristics and microbiology in pilonidal abscesses in children

    Pilonidal abscesses often infected, recurrence unpredictableRetrospectiveLow quality

    154 people10-year period

    anaerobic bacteria and Streptococcus anginosus group were the most commonly found germs; no patient characteristics were linked to the abscess recurring

    Who was studied
    children with pilonidal abscesses treated at a children's hospital
    Main outcome
    types of bacteria found in pilonidal abscesses and factors linked to the abscess coming back
    Quality
    this is a single-center chart review describing infections and germs with no comparison group, so it can describe what was found but not prove how often abscesses occur or who is at risk.
    Limitations
    Single tertiary pediatric center, retrospective design, no control group, and the abstract states no risk factors for recurrence were identified.

    Taken word for word from the abstract

    • n 216 pilonidal abscess episodes among 154 children
    • population 216 pilonidal abscess episodes among 154 children over a 10-year period at a tertiary pediatric center
    • primaryOutcome described the microbiology of 216 pilonidal abscess episodes among 154 children over a 10-year period at a tertiary pediatric center and assessed patient characteristics associated with recurrence
    • result Anaerobes and Streptococcus anginosus group were the most common organisms isolated from surgical cultures. No risk factors for recurrence were identified.

    J Pediatric Infect Dis Soc · PMID 41454773 · Read it on PubMed ↗

  • Wang et al. 2026

    18 F-FDG PET/CT of Sacrococcygeal Pilonidal Sinus Carcinoma

    Rare cancer formed from cystCase seriesVery low quality

    1 people2026

    the chronic pilonidal sinus progressed to an abscess that drained spontaneously, and the lesion was later confirmed pathologically as pilonidal sinus carcinoma, a rare cancer with poor prognosis

    Who was studied
    a 69-year-old woman with a chronic pilonidal sinus
    Main outcome
    progression of chronic pilonidal sinus to abscess and malignant transformation
    Quality
    this is a single case report, so it cannot show how often this happens, only that it can happen.
    Limitations
    single case report; no information on how common this outcome is or what led to it in this specific patient.

    Taken word for word from the abstract

    • n a 69-year-old woman with a chronic pilonidal sinus
    • population a 69-year-old woman with a chronic pilonidal sinus
    • primaryOutcome that progressed to an abscess and drained spontaneously
    • result confirmed pathologically as pilonidal sinus carcinoma
    • result Pilonidal sinus carcinoma is rare, with a poor prognosis
    • harm a chronic pilonidal sinus that progressed to an abscess and drained spontaneously
    • harm confirmed pathologically as pilonidal sinus carcinoma

    Clin Nucl Med · PMID 40553632 · Read it on PubMed ↗

  • Räisänen et al. 2025

    Chronic occupational paronychia secondary to digital pilonidal sinus from dog grooming

    Caused persistent nail infection needing surgery.Case seriesVery low qualityRelated question

    1 people2025

    The pilonidal sinus caused a chronic nail-fold infection that did not respond to repeated antibiotic treatment and required surgical excision of the sinuses and nail removal before the infection resolved

    Who was studied
    a dog groomer with two digital pilonidal sinuses caused by embedded hair fragments
    Main outcome
    chronic infection of the nail fold (paronychia) caused by the pilonidal sinus
    Quality
    This is a single case report of an unusual digital (finger) pilonidal sinus in one worker, so it gives very weak evidence about the risks of pilonidal disease in general.
    Limitations
    Only one patient; the sinus was located in the finger from occupational hair exposure rather than the usual sacrococcygeal site, and no comparison group or long-term outcome tracking was reported.

    Taken word for word from the abstract

    • n We present a previously unreported case of chronic paronychia with 2 separate digital pilonidal sinuses resulting from multiple embedded hair fragments in the eponychium of a dog groomer, who had been repeatedly treated with antibiotics with no success and ended up having surgical treatment.
    • population We present a previously unreported case of chronic paronychia with 2 separate digital pilonidal sinuses resulting from multiple embedded hair fragments in the eponychium of a dog groomer
    • primaryOutcome chronic paronychia with 2 separate digital pilonidal sinuses
    • result We present a previously unreported case of chronic paronychia with 2 separate digital pilonidal sinuses resulting from multiple embedded hair fragments in the eponychium of a dog groomer, who had been repeatedly treated with antibiotics with no success and ended up having surgical treatment.
    • result At the follow-up, the infection had resolved, and nail growth had resumed.
    • harm Chronic hand infection poses a risk of infection contaminating clients or patients; for example, a veterinarian should not operate with an infected hand.

    J Occup Health · PMID 39676260 · Read it on PubMed ↗

  • Couto-González et al. 2022

    Neoplastic degeneration of chronic sacrococcygeal pilonidal sinus: report of seven cases and literature review

    Rare but can turn cancerous, risky if ulcerated.Case seriesVery low quality

    7 people70.5 months

    Over about 34 years on average, the pilonidal sinus turned cancerous in these 7 men; those whose tumor looked ulcerated had nerve invasion, spread into nearby deep tissue and to lymph nodes, and died after about 7 months, while those with a raised (exophytic) tumor had no local or lymph node spread and were all still alive after an average of 70.5 months of follow-up

    Who was studied
    Men with long-standing (chronic) pilonidal sinus disease who developed a tumor at the site
    Main outcome
    Whether the chronic pilonidal sinus turned into a cancer and how that cancer behaved
    Quality
    This is a small retrospective collection of only seven cases from one hospital with no comparison group, so it cannot show how common this risk is, only that it can happen.
    Limitations
    Retrospective, very small number of cases (7), all from a single institution, selection of only diagnosed cancer cases so true risk/frequency cannot be estimated.

    Taken word for word from the abstract

    • population Seven male patients with a mean age at diagnosis of 64.8 years old were collected.
    • primaryOutcome We pretend to determine the factors that influence in the prognosis of the neoplastic disease assessing clinical features and histological findings.
    • n Seven male patients with a mean age at diagnosis of 64.8 years old were collected.
    • result The patients presenting an ulcerative pattern in the primary tumor showed in all the cases perineural invasion, local deep structures infiltration, and neoplastic dissemination to the regional lymph nodes. All these patients died in an average time of 7 months. On the other hand, patients with exophytic patterns in the primary tumor did not present local invasion or regional nodes affectation. All the cases survive with an average follow-up of 70.5 months.
    • harm Neoplastic degeneration is an uncommon but extremely serious complication of pilonidal sinus (PS) disease.

    Cir Cir · PMID 35636935 · Read it on PubMed ↗

  • Konrad Wroński 2019

    A rare case of squamous cell carcinoma arising from chronic sacrococcygeal pilonidal disease

    Very rare risk of skin cancerCase seriesVery low quality

    1 people2019

    A case of squamous cell carcinoma arising from chronic pilonidal disease is reported; the abstract states this malignant transformation is extremely rare, occurring in less than 0.1% of pilonidal disease cases, with fewer than 100 cases reported in the whole medical literature

    Who was studied
    People with long-standing (chronic) pilonidal cysts, typically young men
    Main outcome
    Malignant transformation of the pilonidal cyst into skin cancer (squamous cell carcinoma)
    Quality
    This is a single case report with no comparison group, so it can only show that malignant transformation can happen, not how often it happens or what raises the risk.
    Limitations
    Single patient case report; no systematic data on risk factors, incidence is only roughly estimated, and no information on outcomes beyond this one case

    Taken word for word from the abstract

    • n This article presents the case of a patient with diagnosed squamous cell carcinoma arising from chronic sacrococcygeal pilonidal disease.
    • population Pilonidal disease is a chronic disorder which is observed in boys and men between ages of 15 and 40 years old in Caucasian race.
    • primaryOutcome Malignant degeneration and carcinoma arising from chronic sacrococcygeal pilonidal disease are observed extremely rare and are described in the group of Marjolin cancer.
    • result The incidence of carcinoma arising in pilonidal disease is less than 0,1% and in the whole medical journals less than 100 patients are reported.

    Ann Ital Chir · PMID 31293248 · Read it on PubMed ↗

  • Keighley et al. 2019

    Pilonidal abscess of the breast

    Abscess recurred, needed surgeryCase seriesVery low qualityRelated question

    1 people2019

    the abscess recurred despite antibiotic therapy and needle aspiration, and the patient needed surgical excision of the abscess cavity

    Who was studied
    a 52-year-old woman who presented via the breast clinic complaining of nipple inversion and pain
    Main outcome
    whether the abscess resolved or needed further treatment
    Quality
    this is a single case report of a very rare, atypical presentation (pilonidal abscess in the breast rather than the usual site), so it cannot show how often this happens in general
    Limitations
    single case report; abscess occurred at an unusual site (periareolar breast) rather than the typical natal cleft location, so findings may not generalise to typical pilonidal disease

    Taken word for word from the abstract

    • population a 52-year-old woman who presented via the breast clinic complaining of nipple inversion and pain
    • primaryOutcome an underlying abscess which recurred despite antibiotic therapy and needle aspiration
    • result revealed an underlying abscess which recurred despite antibiotic therapy and needle aspiration; the patient therefore underwent surgical excision of the abscess cavity
    • n We report a case of periareolar pilonidal abscess in the breast of a 52-year-old woman
    • harm revealed an underlying abscess which recurred despite antibiotic therapy and needle aspiration; the patient therefore underwent surgical excision of the abscess cavity

    BMJ Case Rep · PMID 30936332 · Read it on PubMed ↗

  • Delvecchio et al. 2019

    Squamous carcinoma in pilonidalis sinus: case report and review of literature

    Rare risk of cancer from long-term sinus.Case seriesVery low quality

    1 people5 years

    The incidence of carcinoma arising from a pilonidalis sinus is about 0.1% and the most important risk factor is represented by a chronic abscess from 20-30 years.

    Who was studied
    Patient of 83 years old, that after 30 years had a recurrence of pilonidal sinus revealed by a sacral abscess
    Main outcome
    squamous carcinoma arising from a pilonidal sinus
    Quality
    This is a single case report combined with a literature review, so it cannot show how often this happens or in whom.
    Limitations
    Single patient case report; findings cannot be generalized to all people with pilonidal sinus.

    Taken word for word from the abstract

    • population Patient of 83 years old, that after 30 years had a recurrence of pilonidal sinus revealed by a sacral abscess
    • n We report a case of squamous carcinoma arising from a pilonidal sinus.
    • primaryOutcome We report a case of squamous carcinoma arising from a pilonidal sinus.
    • result The incidence of carcinoma arising from a pilonidalis sinus is about 0.1% and the most important risk factor is represented by a chronic abscess from 20-30 years.
    • result Sacro-coccyxal fistula should be treated early because chronic inflammation can determine neoplastic degeneration.
    • harm pathologic studies revealed a squamous carcinoma

    G Chir · PMID 30771803 · Read it on PubMed ↗

  • Ercil et al. 2018

    Recurrent Pilonidal Sinus Cyst on Penis

    Recurrent infected cyst with dischargeCase seriesVery low qualityRelated question

    1 people2018

    The sinus caused a chronic, recurrent, suppurative and ulcerative skin lesion on the penis infected with Actinomyces israelii bacteria

    Who was studied
    young man with a pilonidal sinus located on the penis
    Main outcome
    whether the pilonidal sinus caused complications such as infection or recurrence
    Quality
    This is a single unusual case report, so it cannot show how often or how severely pilonidal cysts cause harm in general.
    Limitations
    Only one patient is described, the location (penis) is an extremely rare and atypical site for pilonidal sinus, and there is no information on long-term outcome or follow-up.

    Taken word for word from the abstract

    • population A 20-year-old male presented to the urology outpatient clinic with the complaint of a suppurative lesion with discharge on the skin of the penis which had been ongoing for approximately three months.
    • primaryOutcome Clinical examination revealed an indurated, erythematous, ulcerative lesion, 3 cm x 2 cm in size, in the middle of the ventral aspect of the penile shaft.
    • result We present the first case in literature of recurrent pilonidal sinus related to Actinomyces israelii, located on the penis.
    • n A 20-year-old male presented to the urology outpatient clinic

    Arch Iran Med · PMID 29688739 · Read it on PubMed ↗

  • Eberspacher et al. 2017

    Pilonidal disease mimicking anterior anal fistula and associated with posterior anal fistula: a two-step surgery. Case report

    Caused anal fistula and abscessCase seriesVery low quality

    1 peopleabout one month

    the man's pilonidal sinus was misdiagnosed and found to be the origin of an anterior anal fistula, and was associated with a separate posterior anal fistula communicating with the same abscess, requiring two-step surgery to treat

    Who was studied
    a 36-year-old man with pilonidal disease
    Main outcome
    complications arising from pilonidal disease, including fistula formation and misdiagnosis
    Quality
    this is a single patient case report, so it cannot show how often this complication happens or whether it is typical.
    Limitations
    only one patient; no information on how common this presentation is or long-term outcome beyond the described surgery.

    Taken word for word from the abstract

    • population A 36-year old man was referred to our department with an anal fistula with an anterior opening.
    • primaryOutcome only during the surgery we discovered the origin of the anterior fistula from a misdiagnosed pilonidal sinus
    • result only during the surgery we discovered the origin of the anterior fistula from a misdiagnosed pilonidal sinus. There was also a posterior anal fistula in communication with the same abscess of the anterior one.
    • n A 36-year old man was referred to our department
    • followUp After about one month and the fall of the seton we evaluate the good healing of posterior anal fistula

    G Chir · PMID 29442064 · Read it on PubMed ↗

  • Koutserimpas et al. 2017

    Epidural abscess imitating recurrent pilonidal sinus: a case report

    Rare case of severe spinal infection after surgeryCase seriesVery low qualityRelated question

    1 people1 year

    After surgery for a pilonidal cyst, the patient developed a large epidural abscess (spinal infection) extending from the mid-back to the tailbone area, requiring further surgery and IV antibiotics; the case report notes the patient had undiagnosed diabetes at the time.

    Who was studied
    a 33-year-old man with undiagnosed diabetes who had pilonidal sinus surgery
    Main outcome
    serious complication after pilonidal sinus treatment
    Quality
    This is a single patient case report, so it cannot show how often or how likely this complication is for people with pilonidal cysts in general.
    Limitations
    Single case; patient had untreated diabetes, a known risk factor for serious infection, so the finding may not generalize to typical pilonidal cyst patients.

    Taken word for word from the abstract

    • population A 33-year old male, suffering from previously undiagnosed and untreated diabetes mellitus (DM), presented to our emergency department (ER), one month after open surgical treatment of pilonidal sinus, due to weakness and fever.
    • primaryOutcome We present the first case of an epidural abscess imitating pilonidal sinus.
    • result a computer tomogr aphy (CT )scan was performed revealing an epidural abscess extending from the thoracic vertebrae 12 (T-12) to the sacrococcygeal area. At that point he underwent new surgery for drainage of the epidural abscess.
    • harm a computer tomogr aphy (CT )scan was performed revealing an epidural abscess extending from the thoracic vertebrae 12 (T-12) to the sacrococcygeal area.
    • n A 33-year old male

    G Chir · PMID 29205143 · Read it on PubMed ↗

  • Michalopoulos et al. 2017

    Squamous cell carcinoma arising from chronic sacrococcygeal pilonidal disease: a case report

    Can rarely turn cancerous and fatal.Case seriesVery low quality

    1 people9 months after surgery (recurrence), death shortly after

    Chronic pilonidal disease progressed to squamous cell carcinoma, which invaded nearby bone, recurred after treatment, and the patient died

    Who was studied
    A 60-year-old patient with chronic pilonidal sinus complicated by an anal fistula
    Main outcome
    Development of a serious complication (cancer) from long-standing pilonidal disease
    Quality
    This is a single patient case report, so it cannot show how often this happens or to whom, only that it can occur.
    Limitations
    Single case report; no information on how common this complication is or what other factors contributed.

    Taken word for word from the abstract

    • population a 60-year-old patient with a chronic pilonidal sinus complicated by an anal fistula
    • primaryOutcome Rarely, chronic inflammation and recurrent disease leads to malignant transformation, most commonly to squamous cell carcinoma (SCC)
    • result Histological examination revealed moderately to poorly differentiated SCC
    • result Nine months later, recurrence was found in the sacrum and para-aorta lymph nodes and the patient died shortly after
    • harm The development of SCC in chronic pilonidal disease is a rare but serious complication.
    • n a 60-year-old patient

    World J Surg Oncol · PMID 28302173 · Read it on PubMed ↗

  • Karadağ et al. 2016

    Lateral Orbital Wall Destruction Due to Pilonidal Sinus

    Can erode nearby bone if mistreated.Case seriesVery low qualityRelated question

    1 people2016

    The pilonidal sinus, after incomplete removal, caused destruction of the bone in the lateral orbital wall and risked progressing to bone infection (osteomyelitis) if not properly treated.

    Who was studied
    a person with a pilonidal sinus in an unusual location near the eye, who was initially misdiagnosed as having a different type of cyst
    Main outcome
    damage to nearby bone (orbital wall) and risk of bone infection (osteomyelitis) from the pilonidal sinus
    Quality
    This is a single case report of one unusual patient, so it cannot show how often this happens or to whom.
    Limitations
    Single case report from an atypical location (near the eye rather than the usual sacrococcygeal area) following a misdiagnosis and incomplete surgical excision, so it may not reflect the typical course of an untreated pilonidal cyst.

    Taken word for word from the abstract

    • n a patient of a pilonidal sinus in a rare location-the lateral orbital region
    • population The authors' patient was misdiagnosed with an epidermal cyst
    • primaryOutcome the destruction of bone tissue in the lateral orbital wall
    • result the subsequent incomplete excision of the sinus tract led a pilonidal sinus with a high morbidity resulting in the destruction of bone tissue in the lateral orbital wall
    • result It was, therefore, crucial to accurately diagnose and treat before the infection progressed through the bone and caused osteomyelitis.
    • harm the subsequent incomplete excision of the sinus tract led a pilonidal sinus with a high morbidity resulting in the destruction of bone tissue in the lateral orbital wall

    J Craniofac Surg · PMID 27391513 · Read it on PubMed ↗

  • Kushwaha et al. 2015

    A rare case of vulval pilonidal sinus: incidental diagnosis

    Rare site, no cancer found.Case seriesVery low qualityRelated question

    1 people2015

    A pilonidal sinus occurred at an unusual site (the vulva), presenting as a bleeding lesion with chronic inflammation; no dysplasia or malignancy was found

    Who was studied
    a 63-year-old woman with a vulval lesion
    Main outcome
    what a pilonidal sinus/cyst can cause or present as
    Quality
    This is a single case report, so it cannot show how often this happens or to whom.
    Limitations
    Single case; unusual location (vulva) rather than the typical sacrococcygeal site; no information on general risk or frequency of complications from pilonidal cysts.

    Taken word for word from the abstract

    • n A 63-year-old woman presented
    • population A 63-year-old woman presented with a 4-week history of vulval bleeding.
    • primaryOutcome This chronically inflamed fistulous tract together with hair shafts within the wall of the tract were diagnostic of a pilonidal sinus of the vulva.
    • result There was no evidence of dysplasia or malignancy.
    • result The intervening stroma showed granulation tissue with severe active chronic inflammation.

    BMJ Case Rep · PMID 26216921 · Read it on PubMed ↗

  • Kaminska-Winciorek et al. 2015

    The use of dermoscopy in diagnostics of a pilonidal cyst ("jeep disease") - case reports

    Describes look of cyst under skin scope, not its dangers.Case seriesVery low qualityRelated question

    2 people2015

    The two pilonidal cyst nodules showed a whitish/pink background with radial whitish streaks, peripheral dotted vessels, and a small central ulceration; the abstract notes these pink nodules can resemble amelanocytic melanoma, basal and squamous cell carcinoma, pyogenic granuloma, and lymphoma, so dermoscopy must be used carefully to tell them apart

    Who was studied
    people with a nodular type of pilonidal cyst (the "jeep driver's" or "motorcyclist's" nodule)
    Main outcome
    dermoscopic (skin-surface microscopy) appearance of the pilonidal cyst nodules
    Quality
    This is a report of just two cases focused on describing a diagnostic imaging technique, not a study measuring how often complications or dangers occur in people with pilonidal cysts.
    Limitations
    Only two cases; no data on rates of infection, abscess, malignant change, or need for emergency surgery; the mention of cancers is about diseases that can look similar on dermoscopy, not about the pilonidal cyst turning into cancer.

    Taken word for word from the abstract

    • n present dermoscopic features of two nodular pilonidal cysts
    • population a rare variety of nodular pilonidal cysts known as the "motorcyclist's" or " jeep driver's nodule"
    • primaryOutcome present dermoscopic features of two nodular pilonidal cysts in the diagnostic procedure of pink nodular lesions
    • result Dermoscopy reveals an irregular, whitish and pink-colored background, with centrally located confluent, whitish streaks extending within the lesion, radial from the center to the periphery.
    • result may suggest amelanocytic melanoma, basal and squamous cell carcinoma, pyogenic granuloma, lymphoma, pseudolymphoma and even the pilonidal cyst

    Pol Merkur Lekarski · PMID 25815619 · Read it on PubMed ↗

  • Parpoudi et al. 2015

    Is histological examination necessary when excising a pilonidal cyst?

    Cancer can rarely develop in cyst.Case seriesVery low quality

    1 people2015

    the patient developed locally advanced squamous cell carcinoma arising in the pilonidal cyst after the cancer was missed on initial treatment

    Who was studied
    a patient with a pilonidal cyst that was initially misdiagnosed
    Main outcome
    malignant transformation of the pilonidal cyst into cancer
    Quality
    this is a single case report, so it cannot show how often this happens, only that it can happen.
    Limitations
    only one patient is described, and the abstract states malignant transformation of a pilonidal cyst is rare (about 0.1% incidence), so this case may not be typical.

    Taken word for word from the abstract

    • population We present the case of a patient with locally advanced squamous cell carcinoma arising in a pilonidal cyst, due to misdiagnosis of the disease during his first treatment.
    • primaryOutcome Malignant degeneration of a pilonidal cyst is rare, with incidence estimated at 0.1%.
    • result We present the case of a patient with locally advanced squamous cell carcinoma arising in a pilonidal cyst, due to misdiagnosis of the disease during his first treatment.
    • n We present the case of a patient

    Am J Case Rep · PMID 25794794 · Read it on PubMed ↗

  • Esposito et al. 2015

    Squamous cell carcinoma and pilonidal cyst disease

    Can rarely turn cancerous after yearsCase seriesVery low quality

    1 people30 months

    The most frequent complications were cellulitis, abscess formation, and recurrence; cancer (squamous cell carcinoma) developing from the cyst was described as rare, occurring in about 0.02% to 0.1% of cases in the literature

    Who was studied
    a person with long-standing, recurrent pilonidal sinus disease (43-year history)
    Main outcome
    complications that can arise from chronic pilonidal cyst/sinus disease, including infection and cancer change
    Quality
    This is a single patient case report, so it cannot show how often these complications happen in general, only that they can occur.
    Limitations
    Based on one patient's case plus a brief literature mention, not a systematic study of complication rates.

    Taken word for word from the abstract

    • n a 63- years-old patient with a 43 years history of recurrent pilonidal sinus disease
    • population a 63- years-old patient with a 43 years history of recurrent pilonidal sinus disease
    • primaryOutcome The complications that arise most frequently are cellulitis, abscess formation and developments of recurrences.
    • result The complications that arise most frequently are cellulitis, abscess formation and developments of recurrences. Malignant transformation appears rather rare and is reported in the literature with a percentage that goes from 0.02% to 0.1%.
    • followUp After 30 months there were no evidence of recurrence.

    Ann Ital Chir · PMID 25693725 · Read it on PubMed ↗

  • Cruz-Mendoza et al. 2014

    [Moderately differentiated squamous cell carcinoma associated pilonidal cyst]

    Rare risk of cancer in long-standing cystsCase seriesLow quality

    1 people50 years of evolution

    Malignant degeneration of a pilonidal sinus is reported as rare, occurring mainly in chronic, recurrent cases, and the one case described (60-year-old man with 50 years of disease) was later found to be squamous cell carcinoma with a very poor prognosis; a prior review of 367 patients found cancer in 0.81% of cases.

    Who was studied
    People with long-standing pilonidal cysts or sinuses
    Main outcome
    Malignant transformation (cancer) arising from a pilonidal sinus
    Quality
    This is a single case report combined with a small retrospective review, so it cannot reliably estimate how often cancer occurs in pilonidal disease.
    Limitations
    Single patient case report with background data from a separate retrospective review; no systematic follow-up of a defined population.

    Taken word for word from the abstract

    • population patients with simple and complicated pilonidal cysts
    • primaryOutcome Malignant degeneration of pilonidal sinus is a rare complication observed mainly in recurrent chronic cases of the disease
    • result We found three cases (0.81%) of epidermoid carcinoma.
    • result Men's 60 years of age, with clinical picture of 50 years of evolution with the presence of sacral tumor, is resection and histopathological reporting of pilonidal cyst
    • result report is squamous cell carcinoma
    • harm Malignant degeneration of pilonidal sinus is a rare complication observed mainly in recurrent chronic cases of the disease, associated to a very bad prognosis.
    • n In Spain had reviewed 367 patients with simple and complicated pilonidal cysts.

    Cir Cir · PMID 25510796 · Read it on PubMed ↗

  • Mengual-Ballester et al. 2014

    [Presacral tumor as a differential diagnosis of recurrent pilonidal sinus]

    Rare tumor mimicked pilonidal sinusCase seriesVery low qualityRelated question

    1 people2014

    the true cause of his recurrent pilonidal sinus turned out to be a separate presacral (retrorectal) cystic teratoma, not the pilonidal cyst itself

    Who was studied
    a 22-year-old man with a recurrent pilonidal sinus
    Main outcome
    final diagnosis after repeated pilonidal surgery
    Quality
    this is a single case report, so it cannot show how often this happens or apply to people with pilonidal cysts in general
    Limitations
    single patient case report with no follow-up data or information on frequency of this finding

    Taken word for word from the abstract

    • population a 22-year-old male with a pilonidal cyst operated due to recurrent pilonidal sinus cyst
    • primaryOutcome Final diagnosis after pelvic computed tomography is large retrorectal cystic tumor and magnetic resonance diagnosis of a presacral cystic compatible wtih germ cell tumor
    • result The tumor was removed surgically through the abdomen and diagnosis of cystic teratoma was established
    • result Retrorectal tumors are rare lesions whose presence must be ruled out in case of recurrent sinus
    • n a 22-year-old male

    Cir Cir · PMID 25259438 · Read it on PubMed ↗

  • Ardelt et al. 2016

    Microbiology of the infected recurrent sacrococcygeal pilonidal sinus

    Infected sinuses have shifting bacteria typesRetrospectiveLow qualityRelated question

    96 people2016

    Recurrent infected pilonidal sinuses showed a shift in bacteria toward more gram-positive and, to a lesser extent, more aerobic types compared with first-time infections, though either type of bacteria could occur in either group

    Who was studied
    People with a sacrococcygeal pilonidal sinus, either a first-time (primary) case or a recurring case, who had abscess-forming infection
    Main outcome
    Type of bacteria found in swab samples from infected pilonidal sinuses
    Quality
    This is a retrospective review of swab samples from one centre looking only at bacteria type, not at how often infection, abscesses, or complications occur, so it says little about overall danger from a pilonidal cyst.
    Limitations
    Retrospective single-centre design; only covers patients who already had abscess-forming infection, so it does not describe risk in people with an untreated or asymptomatic cyst; no data on malignant transformation or need for emergency surgery.

    Taken word for word from the abstract

    • population swab samples were taken from primary sacrococcygeal pilonidal sinus (pPS) and 23 swab samples of patients with recurring sacrococcygeal pilonidal sinus (rPS)
    • n 73 swab samples were taken from primary sacrococcygeal pilonidal sinus (pPS) and 23 swab samples of patients with recurring sacrococcygeal pilonidal sinus (rPS)
    • primaryOutcome Microbiological findings of swab samples of abscess-forming PS from 2000 to 2010 were evaluated.
    • result Our results show a statistically significant shift of the bacterial flora towards the gram-positive range (P = 0·029) and a shift with tendency towards the aerobic range (P = 0·090). Pathogens of pPS are not always solely anaerobic or gram-negative, and those of rPS not always aerobic or gram-positive.

    Int Wound J · PMID 24758263 · Read it on PubMed ↗

  • Nunes et al. 2013

    Carcinomatous degeneration of pilonidal cyst with sacrum destruction and invasion of the rectum

    Rare: cyst turned cancerous, invaded rectumCase seriesVery low quality

    1 people2013

    The cancer had grown through the sacrum bone and spread to the wall of the rectum, requiring removal of the rectum, sacrum, and a permanent colostomy

    Who was studied
    a person whose pilonidal cyst turned cancerous
    Main outcome
    the cyst degenerating into cancer and invading nearby organs
    Quality
    This is a single patient's case, so it cannot show how often this happens or who is at risk.
    Limitations
    Single case report with no comparison group; cannot estimate how common this complication is.

    Taken word for word from the abstract

    • n We report the case of a patient
    • population a patient with carcinomatous degeneration of pilonidal cyst
    • primaryOutcome Malignant degeneration of pilonidal cysts is rare.
    • result with bulky disease that extended up to the wall of the rectum
    • result The treatment was extended resection, sacrectomy and abominoperineal resection of the rectosigmoid with permanent colostomy.

    An Bras Dermatol · PMID 24346881 · Read it on PubMed ↗

  • Irkoren et al. 2013

    Rare complication after VAC therapy in the treatment of tissue defect due to surgical excision of pilonidal sinus

    Rare case of cancer in sinus woundCase seriesVery low qualityRelated question

    1 people2013

    The patient developed squamous cell carcinoma in the wound, which went undetected after surgery because the dressing was left in place for 5 days instead of the recommended 2 to 3 days.

    Who was studied
    a person who had surgical removal of a pilonidal sinus, with the wound managed by negative pressure wound therapy (NPWT)
    Main outcome
    development of cancer in the pilonidal sinus wound
    Quality
    This is a single case report, so it cannot show how often this happens or apply to pilonidal cysts in general.
    Limitations
    Only one patient is described, there is no comparison group, and the cancer occurred after surgical treatment rather than showing what happens if a cyst is left untreated.

    Taken word for word from the abstract

    • n a 60-year-old patient
    • population referred after excision of a pilonidal sinus, which was managed postoperatively with NPWT
    • primaryOutcome the patient developed squamous cell carcinoma, which was undetected postoperatively
    • result the patient developed squamous cell carcinoma, which was undetected postoperatively, as the dressing was left in place for 5 days
    • harm the patient developed squamous cell carcinoma, which was undetected postoperatively, as the dressing was left in place for 5 days

    J Wound Ostomy Continence Nurs · PMID 24202229 · Read it on PubMed ↗

How we searchedThe exact query, the date it ran, and what came back — so you can run it yourself.
Searched
PubMed · ClinicalTrials.gov · Crossref on 2026-10-29
The exact search — paste this into PubMed to repeat it
("Pilonidal Sinus"[Mesh]) AND (complications[sh] OR "natural history" OR prognosis[tiab] OR abscess OR sepsis OR "malignant transformation" OR carcinoma OR pregnancy[tiab])
PubMed expanded that to: "Pilonidal Sinus"[MeSH Terms] AND ("complications"[MeSH Subheading] OR "natural history"[All Fields] OR "prognosis"[Title/Abstract] OR ("abscess"[MeSH Terms] OR "abscess"[All Fields] OR "abscesses"[All Fields] OR "abscessation"[All Fields] OR "abscessed"[All Fields] OR "abscessing"[All Fields]) OR ("sepsis"[MeSH Terms] OR "sepsis"[All Fields]) OR "malignant transformation"[All Fields] OR ("carcinoma"[MeSH Terms] OR "carcinoma"[All Fields] OR "carcinomas"[All Fields] OR "carcinoma s"[All Fields]) OR "pregnancy"[Title/Abstract])
What came back
559 records found · 200 read · 29 answered the question
Included
  • Human, animal or laboratory studies reporting an outcome relevant to the question
Excluded
  • Records about a different condition or intervention
  • Records reporting no outcome
  • Retracted publications, which are listed but excluded from every count
Limits
  • Details were read from abstracts, not full papers, so anything reported only in a paper's methods section is not captured here.
  • Fields were read from abstracts, not full text, so detail reported only in a paper's methods section is not captured.
  • Evidence strength is adapted from the GRADE framework. It is not a GRADE assessment and was not produced by a GRADE panel.

Automated evidence review — PubMed, ClinicalTrials.gov, Crossref. Search strategy, grading rules and the checks that must pass before anything publishes were written by Allen Kamrava, MD, MBA, FACS, FASCRS, colon & rectal surgery, Beverly Hills. The pages themselves are compiled by software running that method and are not read one by one before publication — saying otherwise would be the one claim here that could not be checked.

How we grade evidence →

  1. 559records came back from the search
  2. 200were read
  3. 29actually answered the question
Risks and safetyReported side effects and who should be careful.
  • Abscess formation and acute infection, sometimes requiring incision and drainage
  • Recurrence after treatment, affecting at least 10% of people after surgical excision and linked to having had an abscess beforehand
  • Rare malignant transformation (squamous cell carcinoma) after years to decades of chronic disease, found in roughly 0.1% to 0.2% of pilonidal patients across studies
  • Very rare life-threatening infection spreading beyond the cyst, including a toxic shock-like illness and a spinal (epidural) abscess, reported in isolated cases
  • Smoking was linked to more frequent abscesses and complications in people with pilonidal disease
Why people askWhat brings people to this question.
  • A pilonidal cyst can look alarming — red, swollen, and painful — which makes people fear it's something worse.
  • Case reports of pilonidal disease turning into cancer circulate online and can cause anxiety, even though this is rare.
  • People who are pregnant worry that infection or treatment could affect the pregnancy, even though no specific data exists.
  • A cyst that keeps coming back after treatment makes people wonder if it's dangerous to leave alone.
Common questionsShort answers, drawn from the same studies.
Is pilonidal cyst dangerous?
For most people, no — it's a local skin problem that can cause pain and swelling but isn't life-threatening. The main complication seen in studies is abscess (infection), which may need drainage. Serious outcomes like widespread infection or cancer are rare and usually follow years of untreated, recurring disease.
Is pilonidal cyst dangerous in pregnancy?
No study in this review looked specifically at pilonidal cysts during pregnancy, so there's no pregnancy-specific risk data available. The general risks — abscess and infection — are the same ones described in the wider population of studies.
Is an infected pilonidal cyst dangerous?
An infected pilonidal cyst (abscess) is the most commonly reported complication in these studies and usually needs drainage, sometimes with antibiotics. Very rarely, case reports describe infection spreading further — such as a toxic shock-like illness or a spinal abscess — but these are isolated cases, not the typical course.
How likely is a pilonidal cyst to turn into cancer?
It's rare. The largest study that checked tissue removed during surgery found cancer in about 1 in 770 patients (2 of 1,505), almost always after many years of chronic, recurring disease in older adults.
When should I see a doctor about a pilonidal cyst?
Studies point to abscess and infection as the main thing to watch for — see a doctor if the area becomes more red, swollen, painful, or you develop fever. A sinus that has been present for many years, keeps recurring, or changes in appearance should also be checked, given the small but real cancer risk described in long-standing cases.
What has changedEvery re-check, and whether it changed the answer.

  1. 2026-10-29

    Re-reviewed under a revised method. 9 new studies · 43 no longer retrieved · evidence strength low → moderate · conclusion signal of harm → not applicable.

    How certain we are changed. The conclusion changed.

This is information, not advice

This page summarises published research. It cannot tell you what is happening in your own body, and evidence changes. If something is bleeding, painful, or new, it is worth being looked at — that is a different question from the one on this page, and a better one to bring to a consultation.

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Automated evidence review — PubMed, ClinicalTrials.gov, Crossref. Search strategy, grading rules and the checks that must pass before anything publishes were written by Allen Kamrava, MD, MBA, FACS, FASCRS, colon & rectal surgery, Beverly Hills. The pages themselves are compiled by software running that method and are not read one by one before publication — saying otherwise would be the one claim here that could not be checked.

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