Extra-Uterine Low-Grade Endometrial Stromal Sarcoma Presenting as a Urinary Bladder Mass: a Case Report with Review of the Literature

Abstract

Endometrial stromal sarcoma (ESS) is a rare uterine neoplasm accounting for 0.2% of all uterine malignancies and around 15% of all uterine sarcomas. ESS is a malignant tumor which originates from invasive proliferation of cells that resemble stromal cells of the normal proliferative endometrium. Patients typically present with abdominal pain and uterine bleeding. Based on their biologic behavior and molecular aberrations, the latest World Health Organization guideline (WHO 2014) classifies the endometrial stromal tumors into endometrial stromal nodule, low-grade endometrial stromal sarcoma (LG-ESS), high-grade endometrial stromal sarcoma (HG-ESS), and undifferentiated endometrial sarcoma (UES) [1, 2]. LG-ESSs usually have low malignant potential with an indolent clinical course. However, they are well known for their late recurrences even in patients with stage I disease. More than one-third of patients with ESS develop a recurrence which necessitates a long-term follow-up. The most common sites of involvement/ recurrences include the ovary, pelvis, abdomen, and less frequently lung and vagina. Extra-uterine ESS (EESS) is a well-documented entity in the literature; however, it is a rare occurrence as a result of malignant transformation of endometriotic implants [3, 4]. ESS in the urinary bladder is extremely rare with less than 10 cases reported in literature till now to the best of our knowledge [5]. We hereby present a case of urinary bladder ESS with its histological, immunohistochemical, and molecular features compatible with a low-grade ESS (LG-ESS).