Uterine sarcoma

Facts

The uterus is pear shaped with the narrow end pointing down. This narrow lower end, which extends into the vagina, is the cervix. The wider upper part is the body of the uterus, or the uterine corpus.

There are three layers to the body of the uterus:

  • Endometrium, the inner lining
  • Myometrium, a thick layer of muscle
  • Serosa, the outer covering, or membrane

Connective tissue called stroma supports the other uterine tissues.

What is uterine sarcoma?

Most cancer in the uterus—more than 95 percent—starts in the endometrium. This is called endometrial cancer or endometrial carcinoma. (“Carcinoma” is the term for cancer that starts in one of the body’s linings or membranes.) We discuss endometrial cancer in its own section of the website.

In rare cases, cancer starts in another tissue of the uterus. Most of these cancers are uterine sarcoma. (“Sarcoma” is the term for cancer that starts not in a body lining but in one of the body’s other tissues, like muscle, bone, fat, or fibrous tissue.) Only about 3% of uterine cancers are uterine sarcoma. Other less common uterine cancers are uterine papillary serous carcinoma, clear cell carcinoma, and carcinosarcoma (also called malignant mixed mesodermal tumors or malignant mixed mullerian tumors).

Uterine sarcoma occurs when cells in the body of the uterus, usually in the muscle layer, begin to grow abnormally. These cells do not respond to regular cell growth, division, and death signals like they are supposed to. They also don’t organize normally. Instead they grow into a tumor, which may break through into other layers of the uterus.

Although the cervix is part of the uterus, cancer that starts in the cervix is referred to as cervical cancer, and it’s discussed in its own section of this website.

This rest of this section is about uterine sarcoma.

Types

About 1,400 new cases of uterine sarcoma are diagnosed each year in this country. The three types of uterine sarcoma are: 

  • Uterine leiomyosarcoma, the most common type, which starts in the myometrium
  • Endometrial stromal sarcoma, a rare type, which starts in the connective tissue that supports the endometrium (endometrial stroma)
  • Undifferentiated sarcoma, a rare type, which is similar to endometrial stromal sarcoma but more aggressive, meaning it grows and spreads more quickly

Risk factors

These factors increase your risk for uterine sarcoma.

  • Having had radiation therapy to your pelvic area before. Radiation therapy can damage the DNA in cells in ways that can lead to cancer later. Some women who have had pelvic radiation develop uterine sarcoma years or decades after receiving this treatment.

  • Being African American. African-American women are about twice as likely to get uterine sarcoma as are women of European or Asian descent. Doctors do not yet know why the risk is different between these groups of women.

  • Being older. Risk for uterine sarcoma goes up as you age.

Signs and symptoms

A possible symptom of uterine sarcoma is abnormal vaginal bleeding, such as bleeding or spotting between periods or after menopause. This symptom is more common with endometrial stromal sarcoma and undifferentiated sarcoma of the uterus than with uterine leiomyosarcoma. Some women have other abnormal vaginal discharge that doesn’t appear to have blood in it.

The following may be signs or symptoms of uterine sarcoma, but they are uncommon:

  • Pain in the pelvic area

  • A mass or a sense of fullness in the pelvic area or abdomen

  • Frequent urination

  • Pain when urinating or having a bowel movement

  • Pain during intercourse

Conditions other than cancer may cause these signs and symptoms. If you have any of these, see your doctor to find out the reason.

Diagnosis

If you have signs or symptoms that could be from uterine sarcoma (or another problem with your reproductive organs), your doctor will probably start by doing a general physical exam and then a pelvic exam.

To diagnose uterine sarcoma, doctors have to remove a small sample of tissue from your uterus and look at the cells under a microscope. Seattle Cancer Care Alliance has a dedicated pathologist who specializes in the diagnosis of gynecologic cancers.

Endometrial biopsy

As part of your work-up, your doctor may do an endometrial biopsy. The doctor inserts a thin, flexible, straw-like tube into your uterus through your cervix and scrapes or suctions out a small amount of endometrium so a pathologist can examine the cells for cancer.

Dilation and curettage

Dilation and curettage (D&C) is another way your doctor can get a sample of cells from inside your uterus. A narrow instrument called a dilator is inserted into your cervix to open it. Next the doctor uses a spoon-like tool called a curette to scrape some tissue from inside your uterus for examination.

Imaging studies

The only way to tell whether you have uterine sarcoma is to examine samples of tissue. In certain situations, your doctor may also want you to have imaging studies to get more information, such as whether your cancer has spread. These might include an X-ray, ultrasound, computed tomography (CT) scan, and magnetic resonance imaging (MRI) scan. 

Stages

Once uterine sarcoma has been diagnosed, doctors perform tests to determine the stage of the cancer. Staging is the process of determining:

  • The grade of your cancer (how abnormal the cells look and how likely the cancer is to grow and spread)

  • Whether (and how deeply) it has invaded other tissues of your uterus

  • Whether it has spread outside your uterus

Doctors use a cancer’s stage as a key factor in making treatment recommendations and estimating a patient’s chance for recovery. For uterine sarcoma, staging is typically done at the time of surgery, which means you and your health care team will probably need to wait until after surgery to make some of your treatment decisions.

The most common staging system for gynecological cancers is the International Federation of Gynecology and Obstetrics (FIGO) 2010 system. This is the system that gynecologic oncologists at Seattle Cancer Care Alliance use.

  • Stage I: Cancer is only in the uterus. It has not spread to any lymph nodes or distant parts of the body.

  • Stage II: Cancer has spread beyond the uterus but not outside the pelvic area. It has not spread to any lymph nodes or distant parts of the body.

  • Stage III: Cancer has spread to the abdomen but not to any lymph nodes or distant parts of the body; or cancer has spread to lymph nodes near the uterus but not to the bladder, rectum, or distant parts of the body.

  • Stage IV: Cancer has spread to the bladder or rectum, lymph nodes outside the pelvis, or organs outside the pelvis, such as the lungs, liver, or bones.