Latent perianal Paget's disease associated with mucin-producing rectal adenocarcinoma. Report of two cases.

Two cases of latent perianal Paget's disease associated with mucin-producing papillary adenocarcinoma of the rectum are described. In both cases, the rectal tumors appeared as polypoid lesions located just above the dentate line. The adjacent anal squamous mucosa showed lateral invasion of alcianophilic mucin-containing Paget cells. Mucin histochemistry revealed the presence of O-acylated and non-O-acylated sialic acids in both neoplastic goblet cells in the adenocarcinomas and Paget cells in the anal mucosa. The Paget cells were immunoreactive diffusely for low-molecular-weight cytokeratin (CAM 5.2) and carcinoembryonic antigen, and focally for CA19-9, epithelial membrane antigen and CA15-3. All these substances were also expressed in the rectal adenocarcinomas but were negative or showed limited expression in the anal squamous epithelium. These findings indicated secondary epidermotropic infiltration of neoplastic goblet cells from the rectal adenocarcinomas.