Endometrial stromal sarcoma with sex cord-like differentiation associated with tamoxifen therapy.

Low-grade endometrial stromal sarcoma with sex cord-like differentiation occurred in two postmenopausal patients who had received tamoxifen for more than 3 years after surgical resection for breast cancer. Uterine sarcomas have been described in association with the use of tamoxifen. Only two cases of endometrial stromal sarcoma with sex cord-like features associated with tamoxifen use have been reported previously. This report adds an additional two cases of this tumor. Immunohistochemical and ultrastructural examinations of the tumor support the concept of smooth muscle differentiation in the sex cord-like areas. This observation proposes that the low-grade endometrial stromal sarcoma with sex cord-like elements may be a consequence of tamoxifen ingestion, but the exact mechanism of tamoxifen in the development of this tumor remains speculative.