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 rare cancer that starts in the muscle and supporting tissues of the uterus (womb).

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

About the uterus

The uterus is a hollow organ, usually about the size and shape of a medium-sized pear:

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

The body of the uterus has 3 layers.

  • The inner layer or lining is the endometrium.
  • The serosa is the layer of tissue coating the outside of the uterus.
  • In the middle is a thick layer of muscle 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 like 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 uterine cancers are carcinomas. If a carcinoma starts in the cervix, it is a cervical carcinoma. Carcinomas starting in the endometrium, the lining of the uterus, are endometrial carcinomas. These types of cancer are covered in Cervical Cancer and Endometrial (Uterine) Cancer.

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. These cancers are also known as malignant mixed mesodermal tumors or malignant mixed mullerian tumors. Uterine carcinosarcomas are covered in Endometrial (Uterine) Cancer.

Types of uterine sarcoma

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

Uterine leiomyosarcoma (LMS)

These tumors start in the muscular wall of the uterus (the myometrium). They are by far the most common type. These tumors can grow and spread quickly.

Endometrial stromal sarcoma (ESS)

ESS tumors start in the supporting connective tissue (stroma) of the lining of the uterus (the endometrium). These cancers are rare.

If the tumor is low grade, the cancer cells do not look very different from normal cells and the tumor tends to grow slowly. Women with low-grade ESS have a better outlook (prognosis) than women with other kinds of uterine sarcomas.

High-grade ESS means the cancer cells look very different from normal cells, and the tumor is growing quickly. This type of ESS is most often found when the tumor is already large and/or has spread. These tumors are hard to treat.

Undifferentiated sarcoma

These cancers may start in the endometrium or the myometrium. They grow and spread quickly and tend to have a poor outlook.

Benign uterine tumors

Several types of benign (not cancer) 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 don't need to be treated. But treatment may be needed if they start causing problems, like 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 American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

National Cancer Institute. Uterine Sarcoma Treatment (PDQ®)–Health Professional Version. July 15, 2015. Accessed at www.cancer.gov/types/uterine/hp/uterine-sarcoma-treatment-pdq on October 26, 2017.

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology. Uterine Neoplasms. Version 1.2018 -- October 13, 2017. 

Potikul C, Tangjitgamol S, Khunnarong J, et al. Uterine Sarcoma: Clinical Presentation, Treatment and Survival Outcomes in Thailand. Asian Pac J Cancer Prev. 2016;17(4):1759-1767

Ricci S, Stone RL, Fader AN. Uterine leiomyosarcoma: Epidemiology, contemporary treatment strategies and the impact of uterine morcellation. Gynecol Oncol. 2017;145(1):208-216.

Last Medical Review: October 12, 2017 Last Revised: November 13, 2017

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