Uterine sarcoma is a rare type of uterine cancer that develops in the muscle and supporting tissues of the uterus.
What is the difference between endometrial cancer and uterine sarcoma?
Though endometrial cancer and uterine sarcoma are both uterine cancers, it’s important to differentiate between them, because they arise from different types of cells, making them distinct in terms of behavior, treatment, and prognosis. When people talk about uterine cancer, they are usually referring to endometrial cancer.
Cancers arising from epithelial tissues are called carcinomas. Endometrial cancer arises from epithelial cells that form the inner lining of the uterus (the endometrium). More than 95% of uterine cancers are endometrial carcinomas.
Cancers arising from supporting tissue, including muscle, fat, bone, or fibrous tissue, are called sarcomas Uterine sarcomas develop in the muscle and supporting tissues of wall of the uterus (the myometrium). Uterine sarcomas are rare.
Screening for Uterine Sarcoma
There is no screening test for uterine sarcoma. The Pap test, a reliable screening tool for cervical cancers, does not screen for uterine sarcoma.
Symptoms of Uterine Sarcoma
Symptoms of uterine sarcoma can include:
- Abnormal bleeding or spotting, such as between periods, more bleeding during periods than normal, and in particular any bleeding that occurs after menopause
- Vaginal discharge
- Pain and/or a mass in the pelvis or abdomen, sometimes accompanied by a feeling of fullness
- Urine or bowel problems, such as more frequent urination, or constipation
These symptoms can be associated with other conditions aside from uterine sarcoma, such as uterine fibroids, precancerous cells in the endometrium, or endometrial sarcoma, and do not necessarily indicate a person has uterine sarcoma. However, if you experience these symptoms, it is recommended that you see a doctor as soon as possible and talk to them about uterine sarcoma and endometrial cancer.
Risk Factors for Uterine Sarcoma
Risk factors for uterine sarcoma include:
- Pelvic radiation therapy, which is sometimes used to treat cervical or rectal cancers, is associated with increased risk of uterine sarcoma, typically 5 to 25 years after the radiation treatment
- Congenital (heritable) retinoblastoma, a cancer of the eye
- Tamoxifen use is associated with a slightly increased risk of uterine sarcoma, but sarcoma is very rare even among women who use tamoxifen
Types of Uterine Sarcoma
There are several different types of uterine sarcoma, which are categorized according to the type of cell from which they originate. Types of uterine sarcoma include:
- Uterine leiomyosarcomas (LMS) are the most common type of uterine sarcomas. LMS starts in the thick layer of the muscle, called the myometrium, that makes up the walls of the uterus.
- Endometrial stromal sarcomas (ESS) develop from the stroma, which is the connective tissue of the endometrium. Low-grade ESS tumors tend to grow more slowly, and patients with low grade ESS tend to have better outcomes. High-grade ESS tumors grow quickly, often making them more difficult to effectively treat.
- Undifferentiated sarcomas can develop from the myometrium or the endometrium, may grow rapidly, and tend have a poor prognosis.
- Adenosarcoma is made up of both gland cells and stromal cells. This type of tumor tends to grow slowly, and has a good prognosis.
Diagnosing Uterine Sarcoma
If a doctor suspects uterine sarcoma, they may recommend further testing and a biopsy. Tests to investigate and confirm a uterine sarcoma diagnosis can include:
- Transvaginal ultrasound is an imaging test performed with a probe that is inserted into the vagina. A transvaginal ultrasound can provide a picture of a tumor or lump in the uterus, but cannot definitively determine if the mass is malignant.
- Tissue sampling, usually at surgery, is needed to confirm a uterine sarcoma diagnosis. Endometrial biopsies are less effective at finding sarcomas, because sarcomas may arise in the wall of the uterus, instead of in the endometrial lining.
- Computed tomography (CT) is an x-ray imaging test that can help show if cancer has spread to other areas of the body. A CT scan may also be used in a CT-guided needle biopsy, which involves a doctor inserting a needle through the skin to remove a tissue sample for further examination. A CT-guided biopsy cannot be used for uterine tumors, but may be performed on other areas of suspected cancer spread.
- Magnetic resonance imaging (MRI) uses radio waves and a magnetic field to provide images of the abdominal or pelvic organs to look for evidence of cancer spread.
- Positron emission tomography (PET) scans involve injection of a slightly radioactive form of sugar, called FDG, through an IV. The FDG collects in cancer cells, which may help cancer to show up more clearly in imaging. PET scans may be performed at the same time as CT scans.
- Chest x-rays can sometimes identify cancer that has spread to the lungs.
Uterine Sarcoma Stages
Uterine sarcoma stages range from stage 1 (I) to stage 4 (IV). The stage refers to how far the cancer has spread. In general, a lower number stage means the cancer has not spread as far, where a higher number stage indicates significant spread. View the American Cancer Society’s detailed information on uterine sarcoma stages.
Treating Uterine Sarcoma
Frontline treatment of uterine sarcoma typically consists of surgery to remove the cancer, followed by radiation, chemotherapy, or hormone therapy to reduce the likelihood of the cancer returning. If a sarcoma is suspected based on imaging, then surgery should be performed by a gynecologic oncologist.
There are a few different types of surgery that may be performed to remove uterine sarcoma and any nearby spread:
- A total hysterectomy (removal of the whole uterus and cervix); radical hysterectomy (removal of the uterus and surrounding tissues, plus part of the upper vagina); bilateral salpingo-oophorectomy, or BSO (removal of both fallopian tubes and ovaries); or lymph node surgery (to determine whether cancer has spread to these sites). Doctors may also perform tumor debulking, which is removal of any additional tumors throughout the abdomen; omentectomy, which removes fatty tissue near the bowel; peritoneal biopsy, which removes peritoneal tissue for biopsy; or a pelvic washing, to collect fluid from the abdominal and pelvic cavities for analysis to look for evidence of cancer spread to these sites.
In addition to (or in place of) surgery to remove uterine sarcoma, treatment may include:
- Radiation therapy, targeting areas of the body where cancer was found, to lower the chances of cancer returning. Radiation therapy may also be used alone or in combination with chemotherapy, when a patient is unable to, or chooses not to, undergo surgery.
- Chemotherapy after surgery, called adjuvant therapy, to reduce the chances of cancer recurring. Chemo may also be used as sole therapy or in combination with radiation therapy, to reduce or prevent spread, or alleviate symptoms.
- Hormone therapy, which is mainly used to treat low-grade endometrial stromal sarcomas (ESS).
- Targeted drug therapy, medicines that target certain proteins or genetic markers to destroy cancer cells.
- Immunotherapy, which aims to enable a patient’s own immune system to destroy cancer cells, may be an option for some uterine tumors based on their genetic profile.
The type of treatment recommended will be based on cancer type and stage, as well as the patient’s overall health, circumstances, and goals of care.
Uterine Sarcoma Recurrence
If cancer comes back, it is called a recurrence. Recurrent uterine sarcoma may come back within the pelvis, which is called a local recurrence. Or, it may return in a distant area such as the lungs or liver. A recurrence in an area far from the original cancer site is called a distant recurrence. Recurrent uterine carcinoma is typically treated the same way as stage 4 (IV) cancer. If cancer recurs, it is important for patients to discuss goals of treatment and care with their medical team.
Some patients who experience a uterine carcinoma recurrence may wish to participate in a cancer clinical trial.
Uterine Sarcoma Incidence
Uterine sarcomas are a rare gynecologic cancer and a rare cancer in general, making up 2% to 5% of all uterine cancers. Uterine sarcomas most typically affect those over age 40, and the average age of someone diagnosed with uterine sarcoma is about 60 years old.