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

Malignant degeneration of pilonidal cysts is rare. The most common histologic type is the squamous cell carcinoma, triggered by the chronic inflammatory process. The growth of the lesion is typically slow. The diagnosis must be early and the appropriate treatment is ample surgical resection, including the presacral fascia. In some cases, as the present one, the diagnosis is made at a stage when the disease has progressed and invaded adjacent structures. In these cases the surgery involves multiple organ resection. We report the case of a patient with carcinomatous degeneration of pilonidal cyst, with bulky disease that extended up to the wall of the rectum. The treatment was extended resection, sacrectomy and abominoperineal resection of the rectosigmoid with permanent colostomy.