Cancer of the anus.

Cancers of the anus, whether keratinizing squamous, nonkeratinizing, clear-cell, or melanoma, are infrequent neoplasms. Small keratinizing (<4 cm2) with no deep invasion can be controlled by local excision or laser ablation, but larger ones may be treated by chemoirradiation, restricting abdominoperineal resection to recurrences. Neither melanomas nor clear-cell cancers are curable, and local control is the surgical objective. Prophylactic groin dissection is not required but, for enlarged nodes or in the presence of a positive sentinel node biopsy, may be curative in many cases and palliative in all.