Cloacogenic cancer of the anorectal junction

Abstract

Summary and Conclusions Highly malignant and distinctive transitional cell tumors of the anorectal area can arise from inconstant and persisting embryologic entodermal cloacal vestiges situated just above the dentate line. These nonkeratinizing lesions are quite similar histologically to the transitional cell tumors found in the cloacogenic portion of the lower genitourinary tract. Microscopic features of these junctional tumors vary somewhat, depending on the site of origin from the complex cloacogenic zone and the mixed epithelial components involved. The cellular patterns of the transitional cell anorectal tumors differ distinctly from the more common rectal adenocarcinoma, the keratinizing squamous cell tumor of the anal canal and the very rare basal cell perianal skin lesion. Most of the cloacogenic upper anal canal and lower rectal junctional lesions occur in women. Many of the reported transitional cell anorectal lesions have metastasized rapidly. The prognosis appears to be graver than that of more common rectal adenocarcinoma and the keratinizing squamous cell anal lesion. Early diagnosis and prompt radical surgical removal seem to offer the best hope for survival.