Epidermoid carcinoma complicating chronic osteomyelitis of the femur.

A case of epidermoid carcinoma of the femur that arose in an area affected with chronic osteomyelitis for over 40 years is reported. The incidence of this rare complication has been estimated at 0.23% to 1.6% of all cases of chronic osteomyelitis. Although cases of sarcoma, adenosarcoma, plasmocytoma, and malignant fibrous histiocytoma have been reported, epidermoid carcinoma is the most common cancer type. This tumor develops after 20 to 40 years of chronic infection with a discharging fistula. Epithelialization of the fistulous tract has been demonstrated. The cancer arises in the metaplastic epithelium and can secondarily spread to the bone. Despite the low grade of malignancy of many of these epidermoid carcinomas, pulmonary metastases are not rare. Amputation meeting criteria for oncologic surgery is the only means of ensuring a good prognosis.