Malignant giant cell tumor associated with leiomyosarcoma of the uterus.

A unique association of uterine malignant giant cell tumor (MGCT) with leiomyosarcoma (LMS) is described. Contrary to the true mixed sarcomas, they appeared as two adjacent tumors with distinctly different gross, histologic, ultrastructural, and immunohistochemical features and little intermixing at their border. The dissemination of MGCT resulted in the fatal outcome 81 days after hysterectomy. Malignant giant cell tumor and LMS were coexistent neoplasms, which derived probably from different progenitor cells. It is suggested that MGCT could develop in association with preexisting LMS.