Abstract

This report describes a uterine tumour exhibiting areas of both endometrial stromal and smooth muscle differentiation. There was extensive intravasular permeation within the myometrium as well as extrauterine vascular involvement. The endometrial stromal component had a myxoid appearance and the smooth muscle component exhibited the typical features of intravenous leiomyomatosis. An additional feature was the presence of numerous benign endometrial-type glands within the neoplasm. In many areas a “zoning” phenomenon was present, with endometrial glands surrounded by endometrial stroma, which was in turn surrounded by smooth muscle. This unique combination of endometrial glands, endometrial stroma, and smooth muscle has, to the best of our knowledge, not been described previously and adds to the morphological spectrum of mixed endometrial stromal-smooth muscle tumours. This report discusses the differential diagnosis of this lesion, which has been designated a low grade endometrial stromal sarcoma with smooth muscle and glandular differentiation.