Uterine Cancer Types: Uterine Sarcoma

Uterine sarcoma is a rare form of uterine cancer that accounts for 3–7% of all uterine cancers. It originates from the muscles and supporting tissues of the uterus. Uterine sarcoma is characterized by aggressive tumor growth and early metastatic potential and is often associated with a poor prognosis. Mortality rates for uterine sarcoma are significantly higher than those of endometrial cancer. Hence, prompt diagnosis and timely treatment are essential for improving patient outcomes.

Uterine sarcoma is typically classified based on histologic types. This distinguishes the types of uterine sarcoma based on the type of cell from which they originate. These histologic types are:

• Uterine leiomyosarcoma (LMS): Tumor arises from the smooth muscle layer (myometrium) of the uterus. It is the most common and aggressive subtype of uterine sarcomas.
• Endometrial stromal sarcoma (ESS): Tumor arises from the supporting connective tissues (stroma) of the uterus. It is often given a grade which provides insights into how aggressive the tumor might be. Low grade ESS is usually slower growing and has a better prognosis.
• Undifferentiated uterine sarcoma (USS): Tumor lacks any distinct cell features and does not resemble any uterine tissue. It originates in the endometrium or myometrium. It is highly aggressive and associated with a poor prognosis.
• Adenosarcoma: Tumor contains a mix of benign tissue and cancerous muscle/connective tissue. It has a slow growth pattern and is associated with a better outlook.

The subtype of uterine sarcoma influences the cancer’s behavior, prognosis and response to treatment. Hence, understanding the different types of uterine sarcomas is important in ensuring appropriate and effective treatment.

The prognosis of uterine sarcoma is closely associated with its subtype, stage and grade at which it is diagnosed. Generally, low-grade ESS and localized tumors (low stage uterine sarcoma) have a better prognosis.

According to the Surveillance, Epidemiology, and End Results (SEER) database, the five-year relative survival rates for uterine sarcoma estimated based cases from 2012–2018 are:

The SEER database classifies five-year relative survival rates into three stages based on the extent of cancer spread.

Learn more: Uterine Cancer: Prognosis and Survival Rates

Although the cause of uterine sarcoma remains unclear, several risk factors have been associated with the disease. These include:

• Pelvic radiation therapy: Women who have undergone radiation therapy to the pelvis have a higher risk of developing uterine sarcoma.
• Tamoxifen use: Use of tamoxifen increases the risk of developing uterine sarcoma.
• Obesity: Obesity increases the risk of developing uterine sarcoma.
• Age: Older women are more prone to developing uterine sarcoma.
• Medical conditions: Certain medical conditions such as diabetes are associated with a greater risk of developing uterine sarcoma.
• Genetics: Women with a specific family history of kidney cancer are more prone to developing uterine sarcoma. This is driven by a rare inherited genetic condition called Hereditary Leiomyomatosis and Renal Carcinoma syndrome (HLRCC).

Early detection of uterine sarcoma poses a challenge as they often present symptoms that are similar to that of benign uterine conditions. Common symptoms include:

• Abnormal vaginal bleeding/discharge
• Pelvic pain
• Abnormal swelling, typically as a noticeable mass in the uterus
• Bowel problems

As these symptoms are not exclusive to uterine sarcoma, seeking timely medical attention is crucial to understand the underlying cause.

Initial diagnosis of uterine sarcoma involves the use of imaging and sampling methods to identify abnormal tissue growth. Imaging methods such as transvaginal ultrasound (TVUS) and magnetic resonance imaging (MRI) are used to detect the presence of tumor growth in the uterus. If abnormalities are detected, a biopsy is carried out to obtain tissue samples and confirm the presence of cancer.

However, a definitive diagnosis of uterine sarcoma can only be obtained post-surgery due to limitations in imaging and sampling techniques. Imaging techniques cannot reliably differentiate between a benign tumor and a malignant sarcoma. A biopsy only samples the uterine lining, often missing tumors in the muscles or supporting tissues of the uterus. Typically, only ESS can be identified through a biopsy as it arises closer to the uterine lining. Hence, surgery is normally performed first to remove the tumor. The removed mass is subsequently analyzed to determine if it is uterine sarcoma.

Learn more: Diagnosing Uterine Cancer

The primary treatment approach for uterine sarcoma is surgery (hysterectomy). In most cases, only the uterus is removed. However, more severe cases of uterine sarcoma may require nearby organs and structures to be removed as well. Adjuvant therapy may also be required post-surgery for late-stage cancers to prevent recurrence and kill off remaining cancer cells. These treatment methods include:

• Radiation therapy: Typically carried out post-surgery to prevent recurrence. It can also be used as a main treatment option for patients who are not suitable to undergo surgery.
• Hormone therapy: Usually only used to treat low-grade ESS as it is more receptive to hormones.
• Chemotherapy: Often used to treat late-stage uterine sarcoma or cancer that has metastasized. It can also be used to relieve symptoms for patients who cannot undergo surgery.

Treatment approaches vary depending on the histological subtype, stage and grade of uterine sarcoma. Hence, it is crucial to work together with your healthcare providers to find the best treatment option for your condition.

Learn more: Uterine Cancer Treatments