Transitional cell cancer of the anus and rectum.

A study was made of all cases of transitional cell cancer of the anus or rectum in the records of the University of California Medical Center, San Francisco. None was listed until 1945, then an additional seven between 1954 and 1960. During the latter period there were 192 cases of adenocarcinoma of the rectum, six cases of squamous cell or epidermoid rectal cancer and 12 cases of squamous cell cancer of the anus.Distinctive and highly malignant anal and rectal epithelial tumors will occasionally arise at or near the anorectal junction from inconstant embryologic entodermal cloacal vestiges. These atypical nonkeratinizing lesions are very similar microscopically to transitional cell tumors found in the cloacogenic portions of the lower genitourinary tract. Review of the literature indicates that the prognosis of cloacogenic anal and rectal lesions appears to be relatively graver than that for the more common adenocarcinomas and keratinizing squamous cell epitheliomas. Early diagnosis and prompt, radical excision seem to offer the only hope for survival.