Uterine sarcoma is a rare and aggressive cancer originating from the muscle or connective tissues of the uterus, unlike the more common endometrial carcinoma, which arises from the inner lining (endometrium). Accounting for only 2% to 5% of all uterine malignancies, this disease is characterized by rapid growth and a higher risk of systemic spread. Specialized diagnostic and treatment approaches are necessary due to its unique cellular origins.
Understanding the Subtypes of Uterine Sarcoma
The behavior and prognosis of uterine sarcoma depend on the specific cell type of origin. The most common subtype is Leiomyosarcoma (LMS), which develops from smooth muscle cells in the myometrium (the thick muscular wall of the uterus). LMS is the most aggressive form, often growing and spreading quickly via the bloodstream to distant sites.
Another group is Endometrial Stromal Sarcoma (ESS), arising from the connective tissue (stroma) of the endometrium. Low-grade ESS is an indolent tumor characterized by slow growth. Conversely, high-grade ESS and Undifferentiated Uterine Sarcoma (UUS) are much more aggressive.
UUS is the rarest subtype, defined by disorganized, poorly differentiated cells that lack the features of muscle or endometrial stromal tissue. UUS often presents with rapid growth and a poor prognosis. Therapeutic strategy must be personalized based on this precise pathological classification.
Identifying Symptoms and Risk Factors
The signs of uterine sarcoma are often vague and can mimic benign conditions, such as uterine fibroids, complicating early recognition. The most common sign is abnormal vaginal bleeding, manifesting as postmenopausal bleeding or unusually heavy bleeding between periods.
Other signs include a rapidly enlarging uterine mass, pelvic pressure, fullness, or abdominal discomfort as the tumor presses on surrounding structures. Because these symptoms are non-specific, the disease is sometimes only detected at an advanced stage.
While the exact cause is unknown, certain factors increase risk. A history of prior pelvic radiation therapy is a known risk factor, with sarcomas sometimes developing five to 25 years later. Long-term use of the anti-estrogen drug tamoxifen, particularly for breast cancer treatment, is associated with an increased risk for the ESS subtype.
Diagnostic Procedures and Staging
Confirming a diagnosis requires obtaining a tissue sample, as imaging cannot distinguish a sarcoma from a benign mass like a fibroid. Standard endometrial biopsies are often insufficient because leiomyosarcomas originate deep within the muscular wall. Therefore, a definitive diagnosis is frequently made only after surgical removal of the mass or a hysterectomy.
Once the diagnosis is confirmed, a comprehensive metastatic workup is performed using imaging technologies like computed tomography (CT) scans and magnetic resonance imaging (MRI). These scans check for spread to other organs, most commonly the lungs, liver, and bones.
This information is used to assign a stage to the cancer, which guides treatment planning and predicts prognosis. Uterine sarcomas are staged using the International Federation of Gynecology and Obstetrics (FIGO) system, ranging from Stage I (confined to the uterus) to Stage IV (spread to distant sites).
Primary Treatment Modalities
Surgery is the foundation for treating localized uterine sarcoma. The procedure most often performed is a total hysterectomy combined with a bilateral salpingo-oophorectomy (removal of the uterus, fallopian tubes, and ovaries). Complete surgical removal of all visible disease is the most important factor influencing long-term survival.
After surgery, adjuvant therapies may be recommended to reduce recurrence risk. Radiation therapy may be directed at the pelvis for localized tumors. Systemic chemotherapy is often utilized for patients with high-grade tumors or disease that has spread beyond the uterus, particularly Leiomyosarcoma.
Hormone therapy is reserved primarily for the Endometrial Stromal Sarcoma (ESS) subtype, as these tumors often express estrogen and progesterone receptors. Agents that block estrogen action, such as aromatase inhibitors or progestins, can slow the growth of hormone-sensitive ESS. Adjuvant therapy selection depends on the specific sarcoma subtype, disease stage, and patient health.