Müllerian adenosarcomalike tumor of the seminal vesicle. A case report with immunohistochemical and ultrastructural observations.

A müllerian adenosarcomalike tumor of the seminal vesicle is described in a 49-year-old man. The tumor occupied the entire right seminal vesicle and adhered to the right lobe of the prostate, in the area adjacent to the seminal vesicle. The tumor was also adherent to the rectum. Microscopically, the cells were seen to invade the prostatic tissue. The tumor consisted of a highly cellular stroma with spindle-shaped pleomorphic cells, suggesting the diagnosis of a low-grade sarcoma. In addition, dilated cystic spaces lined by columnar epithelium were seen. Immunohistochemically, most tumor cells showed positivity for vimentin, desmin, and muscle-specific actin, suggesting smooth-muscle cell differentiation. Furthermore, electron microscopy also demonstrated smooth-muscle differentiation of the tumor cells. The patient has been disease-free for 48 months since undergoing a cystoprostatetectomy.