Late effects of untreated pilonidal cysts and tailbone fistulas are extremely rare and can be divided into two groups: bacterial inflammatory and in extremely rare cases also malignant diseases.
Bacterial inflammatory diseases
Very rarely untreated tailbone fistulas can lead to serious infectious diseases. This includes necrotizing fasciitis, a very violent death of the surrounding soft tissue caused by bacteria, which requires an almost emergency surgical removal of the dead tissue. A rare complication has been described as osteomyelitis (bone inflammation) in the lumbar spine and severe pyomyositis (purulent muscle inflammation), each caused by an infected tailbone fistula.
Malignant transformation
Although the development of malignant changes on the base of a tailbone fistula is very rare, case descriptions appear time and again in medical literature. There are currently around 60 known cases worldwide, the most recent publication dates from 2009. The majority of patients are men with an average age of 52 years. The patients suffered from a symptomatic fistula for an average of 22 years. The carcinomas were observed both in completely untreated patients and in patients who had undergone multiple unsuccessful excisions of the fistula system.
Literature sources:
Velitchkov N, Djedjev M et al (1997) Toxic shock syndrome and necrotizing fasciitis complicating neglected sacrococcygeal pilonidal sinus disease: report of a case. Dis Colon Rectum 40:1386–1390
Verdú A, GarcíaGranero E et al (2000) Lumbar osteomyelitis and epidural abscess complicating recurrent pilonidal cyst: report of a case. Dis Colon Rectum 43:1015–1017
Lorenz U, Abele-Horn M et al (2007) Severe pyomyositis caused by Panton Valentine leucocidinpositive methicillinsensitive Staphylococcus aureus complicating a pilonidal cyst. Langenbecks Arch Surg 392:761–765
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Sharma D, Pratap A et al (2009) Malignant transformation of a pilonidal sinus. Surgery 145:243– 244
Bree E de, Zoetmulder FA et al (2001) Treatment of malignancy arising in pilonidal disease. Ann Surg Oncol 8:60–64
Cleveland BR, Green WO Jr (1964) Squamous cell carcinoma arising in a pilonidal sinus. Surgery 55:381–386
Schubert H (1939) Karzinomatöse Entartung von Steissdermoiden. Zentralbl Chir 66:2098
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