Cotyledonoid dissecting leiomyoma of the uterus. The Sternberg tumor.

We report four cases of an unusual uterine smooth muscle neoplasm. All patients were of reproductive age, ranging from 23 to 41 years old, and had a pelvic mass or an enlarged uterus. Two also had menstrual irregularities. At laparotomy, an exophytic congested bulky tumor resembling placental tissue extended from the uterine wall into the broad ligament and pelvic cavity. In one case the tumors were bilateral but unequal in size. On gross examination, these exophytic components were the most distinctive feature. On microscopic examination the basic lesion appeared to be a dissecting leiomyoma with growth at its periphery in sinuous dissecting patterns and extensive degenerative changes. Some microscopic features, including dissecting growth patterns, distinctive connective tissue alterations, and a rich component of vessels, overlap with those seen in several leiomyoma variants, including infiltrating leiomyoma, leiomyoma with perinodular hydropic degeneration, and intravenous leiomyomatosis. An intravascular component was not a feature. The distinctive gross appearance and microscopic features are embodied in the designation, "cotyledonoid dissecting leiomyoma." The follow-up information available for three cases supports the benign nature of the tumor.