Rectal carcinoma associated with pagetoid phenomenon.

A 64-year-old woman was referred to our hospital with complaints of erosion in the anal region and rectal bleeding. The histopathological examination revealed Paget cells in an epidermis lesion of the skin and rectal carcinoma. The cells were positive for PAS, CEA, and CK20, and negative for GCDFP15 and CK7. Electron microscopic examination revealed the presence of many microvilli in the epidermal Paget cells as well as in the tumor cells and rectum itself. The results suggested that electron microscopy is a very useful technique to differentiate extramammary Paget's disease and pagetoid phenomenon. In the present case, the perianal skin lesion was proved to be due to intraepidermal spread of the rectal carcinoma, or so-called pagetoid phenomenon.