Uterine Cancer: Introduction

Approved by the Cancer.Net Editorial Board, 09/2020

ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Uterine Cancer. Use the menu to see other pages. Think of that menu as a roadmap for this complete guide.

About the uterus

The pear-shaped uterus is hollow and located in a woman’s pelvis between the bladder and rectum. The uterus is also called the womb. It is where a baby grows when a woman is pregnant. The uterus has 3 sections:

  • The cervix, which is the narrow lower section

  • The isthmus, which is the broad section in the middle

  • The fundus, which is the dome-shaped top section.

The uterus is made up of 3 layers: the endometrium (inner layer), the myometrium (the thickest layer composed almost entirely of muscle), and the serosa (the thin outer lining of the uterus).

During a woman's childbearing years, her ovaries typically release an egg every month, and the endometrium grows and thickens in preparation for pregnancy. If the woman does not get pregnant, this endometrial lining passes out of her body through her vagina, a process known as menstruation. This process continues until menopause, when a woman’s ovaries stop releasing eggs.

About uterine cancer

Uterine cancer is the most common cancer occurring within a woman’s reproductive system. Uterine cancer begins when healthy cells in the uterus change and grow out of control, forming a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A benign tumor can grow but generally will not spread to other body parts.

Noncancerous conditions of the uterus include:

  • Fibroids: Benign tumors in the muscle of the uterus

  • Benign polyps: Abnormal growths in the lining of the uterus

  • Endometriosis: A condition in which endometrial tissue, which usually lines the inside of the uterus, is found on the outside of the uterus or other organs

  • Endometrial hyperplasia: A condition in which there is an increased number of cells and glandular structures in the uterine lining. Endometrial hyperplasia can have either normal or atypical cells and simple or complex glandular structures. The risk for developing cancer in the lining of the uterus is higher when endometrial hyperplasia has atypical cells and complex glands.

There are 2 major types of uterine cancer:

  • Adenocarcinoma. This type makes up more than 80% of uterine cancers. It develops from cells in the endometrium. This cancer is commonly called endometrial cancer. One common endometrial adenocarcinoma subtype is called endometrioid carcinoma. Treatment for this type of cancer varies depending on the grade of the tumor, how far it goes into the uterus, and the stage or extent of the disease (see Stages and Grades). Less common subtypes of uterine adenocarcinomas include serous, clear cell, and carcinosarcoma. Carcinosarcoma is a mixture of adenocarcinoma and sarcoma (see below).

  • Sarcoma. This type of uterine cancer develops in the supporting tissues of the uterine glands or in the myometrium, which is the uterine muscle. Sarcoma accounts for about 2% to 4% of uterine cancers. Subtypes of endometrial sarcoma include leiomyosarcoma, endometrial stromal sarcoma, and undifferentiated sarcoma. Learn more about sarcoma.

Cancer confined to the uterine cervix is treated differently from uterine cancer. Learn more about cervical cancer in a separate guide on this website. The rest of this section covers the more common endometrial (adenocarcinoma) cancer.

About genetics and family history of uterine cancer

A higher risk for uterine cancers can be inherited, meaning it is passed from generation to generation, or may skip a generation to appear in the next. This happens about 5% of the time. The syndrome most commonly associated with inherited uterine cancer is called Lynch syndrome. Lynch syndrome is also associated with several other types of cancer, including types of colon, kidney, bladder, and ovarian cancers.

When cells divide and multiply, DNA errors can occur. There are 6 proteins in the body that fix these errors. If 1 of these proteins does not work properly, errors in the DNA can accumulate and yield enough DNA damage that cancer may develop. This problem with DNA repair is called mismatch repair defect (dMMR). The main sign of Lynch syndrome is dMMR.

Cancer can be tested for Lynch syndrome through a special staining process called immunohistochemistry (IHC). Most cases of Lynch syndrome are due to deficiencies in 1 of 4 DNA repair proteins. Only these 4 proteins are routinely tested by IHC. If IHC shows that your cancer lacks 1 of these DNA repair proteins or if you have a family history of a cancer associated with Lynch syndrome, discuss this with your doctor and/or talk with a genetic counselor. However, IHC is a screening test, and further genetic tests are needed to confirm a diagnosis of Lynch syndrome. Not all people who have a tumor which lacks 1 or more of these DNA repair proteins has Lynch syndrome. The changes can also be due to a process called DNA methylation, which typically silences 1 of the more common dMMR genes in the tumor.

Family members may wish to be tested, too. People affected by Lynch syndrome should tell their doctors so they can receive increased screening for Lynch-associated cancers, such as more frequent colonoscopies. Other family members may consider preventive surgery for uterine and ovarian cancers.

If you have uterine cancer, ask your doctor if the cancer can be tested for Lynch syndrome and other possible inherited conditions. Learn more about Lynch syndrome in another section on this website.

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If you would like more of an introduction, explore this related item. Please note that this link will take you to another section on Cancer.Net:

The next section in this guide is Statistics. It helps explain the number of people who are diagnosed with uterine cancer and general survival rates. Use the menu to choose a different section to read in this guide.