What Is Uterine Sarcoma?

Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?

Uterine sarcoma is a cancer of the muscle and supporting tissues of the uterus (womb).

Illustration showing the fallopian tubes, body of uterus, vagina and cervix
illustration showing the female reproductive organs including location of endometrium, myometrium, serosa, fallopian tubes, ovaries, cervix and vagina

About the uterus

The uterus is a hollow organ, about the size and shape of a medium-sized pear. It has two main parts:

  • The lower end of the uterus, which extends into the vagina, is called the cervix.
  • The upper part of the uterus is called the body, and is also known as the corpus.

The body of the uterus has 3 layers. The inner layer or lining is called the endometrium. The serosa is the layer of tissue coating the outside of the uterus. In the middle is a thick layer of muscle that is also known as the myometrium. This muscle layer is needed to push a baby out during childbirth.

Cancers of the uterus and endometrium

Sarcomas are cancers that start from tissues such as muscle, fat, bone, and fibrous tissue (the material that forms tendons and ligaments). Cancers that start in epithelial cells, the cells that line or cover most organs, are called carcinomas.

More than 95% of cancers of the uterus are carcinomas. If a carcinoma starts in the cervix, it is called a cervical carcinoma. Carcinomas starting in the endometrium, the lining of the uterus, are called endometrial carcinomas. These cancers are discussed in Cervical Cancer and Endometrial (Uterine) Cancer. This document is only about uterine sarcomas.

Most uterine sarcomas are put into categories, based on the type of cell they developed from:

  • Endometrial stromal sarcomas develop in the supporting connective tissue (stroma) of the endometrium. These cancers are rare, representing less than 1% (1 in 100) of all uterine cancers. These tumors are low grade -- the cancer cells do not look very abnormal and they tend to grow slowly. Patients with these tumors have a better outlook than those with other uterine sarcomas .
  • Undifferentiated sarcomas used to be considered a type of endometrial stromal sarcoma, but since they are more aggressive and are treated differently from low-grade tumors, they are now considered separately. These cancers make up less than 1% of all uterine cancers and tend to have a poor outlook.
  • Uterine leiomyosarcomas start in the muscular wall of the uterus known as the myometrium. These tumors make up about 2% of cancers that start in the uterus.

Another type of cancer that starts in the uterus is called carcinosarcoma. These cancers start in the endometrium and have features of both sarcomas and carcinomas. They can be classified with uterine sarcomas, but many doctors now believe they are more closely related to carcinomas. These cancers are also known as malignant mixed mesodermal tumors or malignant mixed mullerian tumors. Uterine carcinosarcomas are discussed in detail in Endometrial (Uterine) Cancer.

Benign uterine tumors

Several types of benign (non-cancerous) tumors can also develop in the connective tissues of the uterus. These tumors, such as leiomyomas, adenofibromas, and adenomyomas, are also known as types of fibroid tumors. Most of the time, these tumors require no treatment. Treatment may be needed, however, if they start causing problems--- such as pelvic pain, heavy bleeding, frequent urination, or constipation. In some cases, the tumor is removed, leaving the rest of the uterus in place. This surgery is called a myomectomy. Some treatments destroy these benign tumors without surgery, by blocking the blood vessels that feed them, by killing the tumor cells with electric current, or by freezing them with liquid nitrogen. Another option is to remove the entire uterus. This surgery is called a hysterectomy.

The rest of this document is about uterine sarcomas.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Medical Review: May 12, 2014 Last Revised: February 15, 2016

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