Current concepts and controversies concerning the etiology, pathogenesis, diagnosis, and treatment of malignant tumors of the anus.

Malignant disease of the anus is uncommon. Possible predisposing causes include chronic inflammation and a transmissible agent. Epidemiologic studies suggest an increased incidence in homosexuals. With the exception of mucoepidermoid and small-cell carcinoma, the morphology of anal carcinoma has little influence on treatment and prognosis. Site, size of the primary lesion, and the presence of groin metastases are the crucial factors in prognosis. There is no satisfactory method for staging anal carcinoma--the symptoms are nonspecific. Diagnosis is based on histologic examination of biopsy material or tissue obtained from anal operations. The treatment of infiltrating, recurrent, or residual malignant anal lesions is a radical abdominoperineal resection. The addition of a limited obturator and hypogastric lymphadenectomy may be worthwhile. Inguinal lymphadenectomy provides palliation in the treatment of synchronous groin metastases, whereas in cases of metachronous metastases, groin dissection may result in an occasional cure. Small, noninfiltrating, low-grade anal lesions are best treated by either adequate local excision or supervoltage radiotherapy. If borne out, the promising results obtained with the combined chemoradiotherapy for anal cancer followed by local excision of the residuum will radically alter the future management of carcinoma of the anus.