Endometrial stromal sarcoma

Endometrial stromal sarcoma (ESS) is a rare malignant tumor arising from the stromal (connective tissue) cells of the endometrium, the inner lining of the uterus. It belongs to the broader category of uterine sarcomas and is classified into low-grade endometrial stromal sarcoma (LG-ESS) and high-grade endometrial stromal sarcoma (HG-ESS), which differ significantly in their clinical behavior, molecular features, and prognosis. Low-grade ESS is characterized by indolent growth, a tendency for late recurrence (sometimes years or decades after initial diagnosis), and is often associated with specific chromosomal translocations such as JAZF1-SUZ12 (formerly JAZF1-JJAZ1). High-grade ESS is more aggressive and may harbor YWHAE-NUTM2A/B fusions or other genetic alterations. The disease should be distinguished from undifferentiated uterine sarcoma, which carries a worse prognosis. The most common symptoms include abnormal uterine bleeding, pelvic pain, and an enlarged uterus. Some patients may present with a palpable pelvic mass or symptoms related to compression of adjacent organs such as the bladder or rectum. ESS can extend beyond the uterus, involving the ovaries, pelvic peritoneum, and in advanced cases, the lungs. Low-grade ESS frequently expresses estrogen and progesterone receptors, which has important therapeutic implications. The primary treatment for endometrial stromal sarcoma is surgical, typically involving total hysterectomy with bilateral salpingo-oophorectomy. For low-grade ESS, hormonal therapy (such as aromatase inhibitors, progestins, or GnRH agonists) is commonly used for advanced, recurrent, or metastatic disease, given the tumor's hormone receptor positivity. Importantly, tamoxifen and estrogen-containing hormone replacement therapy are generally avoided as they may stimulate tumor growth. Chemotherapy may be considered for high-grade ESS or undifferentiated tumors, though responses are often limited. Radiation therapy may play a role in local control in select cases. Long-term follow-up is essential, particularly for low-grade ESS, due to the risk of late recurrence.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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