EndometriaI StromaI 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. Acta Pathol Jpn 39: 260–265, 1989.