Endometrial cancer is classified into two types:
Type I cancer depends on estrogen for growth (estrogen-dependent) and are sensitive to hormone treatment. They begin as uncontrolled cell accumulation (hyperplasia) in the endometrium. Treatment of this type is often successful.
Type II cancers are estrogen-independent, and therefore do not respond to hormone therapy. They develop in postmenopausal women because of shrinkage of the endometrium during menopause. Treatment outcome for Type II is poor.
Carcinomas are defined as cancers that start in glands. Endometrial cancer is most often a carcinoma, but it can be further classified according to the types of cells involved. The most common form of the cancer, called endometrioid carcinoma, is type I and arises from the surface layer of cells of the endometrium.
Other type I endometrial carcinomas that are less common include mucinous, which originate in mucin-producing cells (mucin is the major component of mucous), and secretory, which affects cells that secrete other compounds.
Type II endometrial carcinomas include uterine papillary serous and uterine clear cell. Like all type II tumors, these are uncommon and aggressive with a high rate of recurrence. A third type II cancer is adenosquamous, which arises from glands and squamous cells that line the uterus.
Type I and type II carcinoma cells appear distinct under the microscope. The former are characterized by extra DNA on chromosome 1 or an extra copy of chromosomes 2, 7, 10, or 12. Sometimes cells even lack chromosome 22. Type II cancers have much more complex chromosomal changes. Tumor cells are also classified into one of three grades, G1, G2, or G3, based on their appearance. The higher the grade, the more aggressive is the cancer.
Unlike carcinomas, sarcomas originate in connective tissue. Endometrial cancer can also be a sarcoma, called endometrial stromal sarcoma, but this is very rare. Uterine carcinosarcoma is a cancer forming from both glands and connective tissue.
- Physical Exam: Endometrial cancer is diagnosed using physical examinations, imaging techniques and biopsies. Physical exams are most effective at detecting cancer in its later stages. By this time, the uterus may have an abnormal shape, size, or consistency. Doctors also check the surrounding organs, such as the vagina and bladder, for any unusual cell masses. They use a speculum inserted into the vagina to examine the upper part of the vagina and cervix.
- Ultrasound: Often a diagnosis is made by using transvaginal ultrasound (ultrasonography). This is used to detect endometrial thickening in postmenopausal women who are experiencing bleeding episodes. In the procedure, an instrument is inserted into the vagina and high-frequency sound waves are directed at the uterus. The resulting echo pattern is displayed on a monitor. If the display suggests the endometrium is thickened, a hydroultrasonogram may be used to confirm the finding. For this, doctors place a small amount of saline into the endometrial cavity and repeat the ultrasound.
- Biopsy: Suspected cases of cancer are followed up with a biopsy. A biopsy is a procedure in which a small sample of cells is removed from the endometrium. Biopsies can be performed in several ways. In the typical endometrial biopsy, the cervix is held open with forceps and a catheter is inserted into the uterus. A small tube inside the catheter, called an internal piston, is pulled to create suction. Tissue is removed as the catheter is moved and rotated. In contrast, aspiration biopsies are performed by sucking cells into a needle. Samples of the entire endometrial surface can be obtained using the commercially-available TruTest. This test obtains cells using an instrument called a Tao Brush.
Less common methods for diagnosis include a Pap smear and a dilation and curettage, in which the cervix is opened (dilated) and a small spoon-shaped implement is used to collect endometrial cells.
Overview of Staging Endometrial Cancer
Staging is used to assess the extent of the cancer and whether it has spread to other parts of the body (a process called metastasis). This information is used to direct treatment and predict outcome. Blood and urine tests, x-rays, ultrasounds, magnetic resonance imaging (MRI), and other imaging techniques are often used to help stage the cancer.
Stages of Endometrial Cancer
Endometrial cancer is placed into one of four stages:
- Stage I: The cancer is limited to the uterus, but has not affected the cervix.
- In stage IA, the tumor is only growing in the endometrium.
- In stage IB, the tumor has penetrated half of the myometrium (outer muscular wall of the uterus). In stage IC, the tumor has spread into more than half the myometrium.
- Stage II: The cancerous cells have spread to the cervix. The substages, stage IIA and IIB, are distinguished by the amount of cervical involvement.
- Stage III: The cancer has spread beyond the uterus but not outside the pelvic region or to the bladder or rectum.
- In stage IIIA, the malignant cells reach the serosa (outermost layer of the uterus) or peritoneum (membrane coating the abdominal cavity).
- In stage IIIB and stage IIIC, the vagina and lymph nodes become involved, respectively.
- Stage IV: The cancer has spread to the bladder or rectum (stage IVA) or other parts of the body outside the pelvic region (stage IVB).