Unusual Presentation of Squamous Cell Carcinoma on Long-Standing Sacrococcygeal Pilonidal Sinus

Pilonidal disease consists of a hair-containing sinus or abscessoccurring most frequently in intergluteal cleft. this disease isgenerally benign. although very uncommon entity, it seemsreasonable to be aware of possible malignancy in longstandingcases. we report a case of squamous cell carcinoma in a 52-year-old man, with a prolonged history of pilonidal diseaseand ulceration since 3 months before referring to our clinic.we excised the cyst, and the pathologic evaluation reportedmoderate differentiated squamous cell carcinoma. so, reoperationon the lesion site to excise a 2-cm margin wasperformed and the defect was covered with limberg cutaneusflap. we recommend early excision of pilonidal cysts toprevent possible malignant degeneration. histologicalexamination of the excised materials to prevent missing raremalignant cases is recommended.iran j med sci 2009; 34(2): 149-151.