Clinicopathologic study of 28 uterine leiomyosarcomas with metastasis.

Twenty-eight smooth muscle tumors of the uterine corpus that exhibited metastasis were studied to determine gross and microscopic features associated with metastasis and potential for metastasis. Seventeen of 28 patients were advanced stage at initial diagnosis, and the other 11 patients developed metastases 3 months to 9 years later. Seventy-nine percent of tumors occurred in women 50 years or older. Size was a feature of metastatic capability, as 22 tumors were larger than 5 cm. Of the six neoplasms smaller than 5 cm, five had increased mitotic activity and cytologic atypia to qualify them as sarcomas. The remaining one with four mitotic figures (MF) per 10 high-power fields (HPF) and 1+ atypia had infiltrative margins and vascular invasion that probably accounted for its aggressive behavior. Sixteen cases were composed predominantly of spindle cells, 10 were epithelioid, and two were myxoid. Cytologic atypia was a prerequisite for metastasis as it was present in all. On a scale of 3, 12 were nuclear grade 3, 15 were grade 2, and one was grade 1. The average mitotic activity was 14 MF/10 HPF, and 86% had > 4 MF/10 HPF. Of the five leiomyosarcomas with low mitotic activity (fewer than 5 MF/10 HPF), three were the spindle cell variety, one was epithelioid, and one was myxoid. An epithelioid cell type occurred in 39% of tumors and is a feature that identifies a neoplasm capable of metastasis, even with low mitotic activity.