Squamous cell carcinoma arising in a cutaneous epidermal cyst--a case report.

INTRODUCTION Cutaneous epidermal cysts are common lesions, but fortunately, malignant transformation of their epithelium is rare. There are only a few cases mentioned in recent literature, mostly occurring in epidermal cysts in the head and neck region. CLINICAL PICTURE We present a case of malignant transformation in a long-standing buttock epidermal cyst, presenting a month after trauma to the cyst. TREATMENT An excision biopsy and rotation flap was done. When the pathology was confirmed, a second resection was carried out and the defect covered with a free latissimus dorsi flap, a buttock rotation flap and a posterior thigh rotation flap. CONCLUSION Although malignant transformation is rare, this case illustrates the importance of routine histology in excision of epidermal cysts.