A malignant tumor of the vagina resembling synovial sarcoma: a light and electron microscopic study.

A malignant tumor arising in the upper lateral vaginal mucosa in a 24-year-old white woman, hitherto undescribed in the literature, was studied by light and electron microscopy. The main part of the tumor was epithelioid, forming a tubular or acinar pattern. At the periphery, the tumor cells were more spindly and formed sheets resembling fibrosarcoma. The tumor cells contained occasional material positive for mucicarmine, alcian blue, and PAS stains, and the nests of the cells forming acini were surrounded by reticulin fibers. The tumor ultrastructure consisted of a single type of cell with large cytoplasmic vacuoles and occasional perinuclear intracytoplasmic filaments. Slender long microvilli projecting into the lumina were also characteristic. Basal laminae were occasionally present around the acini. The findings suggested that the tumor was of mesenchymal origin, closely related to synovial sarcoma.