Uterine cancer types

Uterine cancer, which forms in the uterus or womb, is the most common kind of cancer affecting the female reproductive system. According to the American Cancer Society (ACS), about 66,570 new uterine cancer cases are expected to be diagnosed in the United States in 2021, most commonly among women who have gone through menopause. On average, it’s most often diagnosed at age 60.

Uterine cancer has two primary types that develop in different parts of the uterus:

Endometrial cancer develops in the lining of the uterus, called the endometrium. This is the most common type of uterine cancer, accounting for more than 90 percent of cases.

Uterine sarcoma is a rarer type of uterine cancer that forms in the muscles or other tissues of the uterus.

Endometrial cancer

Endometrial cancer is the most common form of uterine cancer. Because the endometrium is part of the uterus, endometrial cancer is often referred to as uterine cancer. Endometrial cancer is the most commonly diagnosed gynecologic cancer (which includes cancers of the uterus, cervix, ovaries, vulva, vagina and fallopian tubes).

More than 80 percent of all endometrial cancers are adenocarcinomas of the endometrium. This type of cancer forms when cells in the endometrium—the inner lining of the uterus—begin to grow out of control. Endometroid carcinoma accounts for most cases of endometrial adenocarcinoma.

Other types of endometrial cancer include:

Serous adenocarcinoma, which are tumors that are more likely to spread to the lymph nodes and other parts of the body

Adenosquamous carcinoma, a rare uterine cancer that is similar to endometrial adenocarcinoma and carcinoma of the squamous cells that line the outer layer of the uterus

Uterine carcinosarcoma, which has cancer cells that look like endometrial cancer and sarcoma and has a high risk of spreading to the lymph nodes and other parts of the body

Doctors classify the different types of endometrial cancer based on what the cells look like when examined under a microscope.

The five-year relative survival rate of all combined stages of endometrial cancer is 81 percent, according to the Surveillance, Epidemiology, and End Results (SEER) database. However, it varies based on whether the cancer has spread, from 95 percent for localized cancer down to 18 percent if it’s spread to other parts of the body. A five-year relative survival rate for uterine cancer is how long women with the same types and stages of uterine cancer survived during a five-year period, compared with women in the total population.

Uterine sarcoma

Uterine sarcomas, which form in the muscle wall of the uterus, make up less than 4 percent of all cancers of the uterus. Each subtype of uterine sarcoma differs in the way it develops and changes over time, as well as in how it’s treated. Doctors classify uterine sarcomas based on the type of cells in which the cancers begin. These include:

Uterine leiomyosarcoma, the most common type of uterine sarcoma, forms in the muscular wall of the uterus, known as the myometrium, and it makes up about 2 percent of uterine cancers.

Endometrial stromal sarcomas develop in the connective tissue that supports the endometrium. These cancers represent less than 1 percent of all uterine cancers, and typically grow slowly.

Undifferentiated sarcoma, a rare subtype, is similar to endometrial stromal sarcoma, but it’s more aggressive, meaning it grows and spreads more quickly. These cancers make up less than 1 percent of all uterine cancers.

ACS uses data from SEER showing that the five-year survival rates vary based on the type of uterine sarcoma.

• Endometrial stromal sarcoma: 95 percent
• Leiomyosarcoma: 41 percent
• Undifferentiated sarcoma: 43 percent