Primary vaginal adenocarcinoma of intestinal type arising from an adenoma: case report and review of the literature.

A 1 cm polypoid lesion was encountered on the posterior vaginal wall in a 56-year-old woman with no history of diethylstilbestrol exposure that on microscopic examination was a moderately differentiated adenocarcinoma of intestinal type. The tumor was cytokeratin 20 and carcinoembryonic antigen positive and negative for cytokeratin 7. Mucin histochemistry demonstrated the presence of o-acetylated sialomucin, a specific marker of large intestinal differentiation. The initial interpretation favored a metastasis from a colonic adenocarcinoma, but clinical investigations showed no evidence of a primary gastrointestinal lesion. The morphology, histochemical, and differential cytokeratin profile led to the lesion being reinterpreted as a primary intestinal-type adenocarcinoma of the vagina arising from a tubular adenoma. Although a very rare tumor, awareness of this lesion is important as it must be distinguished from metastatic adenocarcinomas from other sites.