Malignant plexiform tumor of the uterus: an unusual variant of epithelioid leiomyosarcoma.

A 46-year-old woman with the complaint of hypermenorrhea underwent hysterectomy for a presumed uterine myoma. The solid tumor in the myometrium was gray in color, was 4 cm in diameter, and showed hemorrhage and necrosis. Histologically, the tumor consisted of round or polygonal cells arranged in cords and nests, and its histological features closely resembled those of plexiform tumor which has been reported as a benign, epithelioid smooth muscle tumor of the uterus. In the tumor in our patient, however, mild nuclear atypia and two to three mitoses/10 high-power fields were present. Two months after the hysterectomy, the patient was found to have metastatic foci in the lumbar vertebrae and iliac bone, which contained tumor cells with the same histological features. Accordingly, the present tumor might be interpreted as a malignant plexiform tumor of the uterus, an unusual variant of epithelioid leiomyosarcoma.