Endometrial stromal sarcoma of low-grade malignancy. Immunohistochemical and three-dimensional reconstruction study with special emphasis on the inadequate terminology of endolymphatic stromal myosis.

We report two cases of endometrial stromal sarcoma of low-grade malignancy (so-called endolymphatic stromal myosis) with special emphasis on the histogenesis and mode of invasion. The microscopic and immunohistochemical features of the tumor cells resembled those of endometrial stromal cells. A three-dimensional reconstruction study of the tumor disclosed that it grew by forming a horn- or crown-like structure between and along the vessels. The tumor then protruded into the vascular lumina with a covering of endothelial cells. Immunohistochemical study showed that the vascular system was not lymphatic but venous. We therefore think that "endolymphatic stromal myosis" is a misnomer.