Adenocarcinoma of the rete testis with a spindle cell component. A possible metaplastic carcinoma.

A case of adenocarcinoma of the rete testis was encountered in a 36-year-old white man. The tumor fulfilled established criteria for determining origin in the rete and showed an unusual biphasic morphology with papillary adenocarcinoma mixed with a prominent component of cytologically malignant spindle cells. Immunohistochemical study demonstrated a positive reaction in the epithelium for cytokeratin and epithelial membrane antigen, and the cytoplasm of a few of the spindle cells also reacted with these antibodies. Electron microscopic study confirmed the biphasic pattern, showing epithelial gland formation and mesenchymal cells. The results indicate that this tumor is a metaplastic carcinoma of the rete testis. Recognition of this pattern of rete carcinoma may further enhance our knowledge of primary tumors at this unusual site.