Endometrial stromal sarcoma is a malignant subtype of endometrial stromal tumor arising from the stroma (connective tissue) of the endometrium rather than the glands. There are three grades for endometrial stromal tumors, as follows. It was previously known as endolymphatic stromal myosis because of diffuse infiltration of myometrial tissue or the invasion of lymphatic channels.

Low-grade endometrial stromal sarcoma

Low-grade endometrial stromal sarcoma consists of cells resembling normal proliferative phase endometrium, but with infiltration or vascular invasion. These behave less aggressively, sometimes metastasizing, with cancer stage the best predictor of survival. The cells express estrogen/progesterone-receptors.

Undifferentiated uterine sarcoma

Undifferentiated uterine sarcoma, or undifferentiated (high-grade) endometrial stromal sarcoma, does not resemble normal endometrial stroma and behaves much more aggressively, frequently metastasizing. The differential includes leukemia, lymphoma, high-grade carcinoma, carcinosarcoma, and differentiated pure sarcomas.

Pathology

Macroscopy

Microscopy

Immunochemistry

Genetic features

A recurrent chromosomal translocation, t(7;17)(p15;q21), occurs in endometrial stromal sarcoma. This translocation leads to the fusion of two polycomb group genes, JAZF1 and JJAZ1, with production of a fusion transcript with anti-apoptotic properties. Even normal endometrial stroma cells express the fusion gene, derived not by translocation, but by the "stitching" together of m-RNAs. Thus, it appears that a pro-survival gene in the normal endometrium is somehow subverted to become pro-neoplastic.