Stromomyoma of the uterus.

We present a solitary uterine tumor that occurred in a 28-year-old woman who complained of vaginal bleeding. Grossly, the tumor was well circumscribed and composed of lobulated tissue that varied from yellow, tan and soft, to white and rubbery. At the light microscopic level, areas identical to those described and interpreted as sex-cord differentiation in a group of closely similar uterine tumors were found and obtained for electron microscopic study. Ultrastructurally, there were two basic types of cells, neither of which can be interpreted as sex-cord derivatives. Cells that closely resembled the predominant components of Clement and Scully's group I tumors were similar to the normal endometrial stromal cells. Cells that formed plexiform cords demonstrated features diagnostic of smooth muscle cells. Cellular contents in cells comprising the tubular structures resembling that interpreted as indistinguishable from that of a Sertoli-cell tumor (tubular androblastoma) were probably smooth muscle cells. We propose the term "Stromomyoma" to designate this peculiar uterine tumor. The similarity between our tumor and those reported in the literature raises the possibility that "uterine tumor resembling" ovarian sex-cord tumors" are actually stromomyomas.