Intravenous leiomyomatosis of the uterus. A clinicopathological analysis of 16 cases with unusual histologic features.

We describe 16 cases of intravenous leiomyomatosis of the uterus with unusual histologic features. Most of the patients, who ranged in age from 28 to 76 years (median, 42 years), presented with abnormal uterine bleeding or pelvic pain. On pelvic examination, they had an enlarged uterus. Extension of tumor into the broad ligament was noted at operation in six patients; it was documented on pathologic examination in an additional three cases. Gross examination disclosed enlargement of the uterus by solitary or multiple masses; wormlike plugs of tumor within myometrial veins were noted on initial examination in only five cases. Histologic examination in each case revealed proliferations of benign-appearing smooth muscle within myometrial vessels, at least some of which were large veins. The tumors differed from typical intravenous leiomyomatosis (IVL). They were classified as cellular IVL (six cases), epithelioid IVL (four cases), IVL with bizarre nuclei (two cases), intravenous lipoleiomyomatosis (two cases), myxoid IVL (one case), and IVL with an endometrial component (one case). Of 13 patients with follow-up information, 11 are alive with no evidence of disease or have died of unrelated causes at postoperative intervals of 0.5 to 19 years. One patient underwent resection of pelvic recurrent tumor 2 years postoperatively and was alive with no evidence of disease 2 years later. Another patient had pulmonary metastases 9 years postoperatively, but was alive with stable disease after an additional 6 years. This analysis indicates that most of the histologic variants of benign uterine leiomyoma can exhibit the intravascular growth pattern of IVL. These variants of IVL, except for their cellular composition, resemble typical IVL in both their clinical and pathological features. They should be distinguished from other tumors, particularly endometrial stromal sarcoma and leiomyosarcoma, which differ in their behavior and management.