Squamous cell carcinoma arising in recurrent pilonidal sinus in an older woman

Malignant transformation is a rare complication of pilonidal sinus. We report the case of a 90-year-old female who had a recurrent pilonidal sinus with fistulous abscess formation. We excised the whole pilonidal sinus because the infection could not be controlled by oral antibiotics. Squamous cell carcinoma (SCC) was found in the sinus tract with a negative surgical margin. A whole abdominal computed tomography scan was performed, which showed no distant metastasis and no enlargement of the bilateral inguinal lymph nodes. This case study illustrates that SCC transformation may present in the recurrent and long-standing pilonidal sinus. We suggested that all pilonidal sinus lesions should be sent for pathologic examination to early detect malignant transformation.