Ano-rectal melanoma

Abstract

The incidence of melanoma of the ano-rectum is discussed and the authors introduce 17 cases from the records of the Armed Forces Institute of Pathology. The anatomy of the ano-rectum is described and some features which lead to difficulties are discussed. Of particular interest are the intermingling of squamous and columnar epithelium in the area and the problems of definition of the anal boundaries. Reasons are given for regarding only 2 of the 17 cases as truly rectal. Clinical details confirm the poor prognosis of this condition; the mean survival of the patients was 15 months. Pathologically, the most common finding was of separated tumors of the squamous and columnar mucosae, often with intervening satellite lesions of the mucosa or submucosa. Seven tumors showed junction change at the squamous mucous membrane. Theories of the histogenesis of melanoma in general are discussed and applied to the material under review. The authors conclude that it is probable that most melanomas of the ano-rectum are primary in the anus with involvement of the rectum by direct or metastatic extension.