In addition to distinguishing them by histology, doctors can think of them as two “types” called Type I and Type II.Type I endometrial cancer is caused by an excess of the hormone estrogen. This excess can be caused by taking unopposed estrogen (estrogen without progesterone), but it can also be caused by obesity because fat cells store hormones that the body converts into estrogen. Women who develop Type I endometrial cancer are often post menopausal (in their sixth decade) and obese. They may suffer from gall bladder disease and have diabetes.
Type I cancers are usually endometrioid type and are usually grade I, or well differentiated. They are often associated with a specific genetic mutation involving a loss of PTEN, which can be checked in a lab under the microscope. Type I cancers also are often associated with a condition of the endometrium called complex atypical hyperplasia, which is thought to be a precursor lesion for endometrioid adenocarcinoma of the endometrium.
Type II cancers, on the other hand, are not associated with excess estrogen, and are usually more aggressive. They occur in women who are older, in their seventh decade and above, and are often high grade, or papillary serous. These cancers have a worse prognosis than Type I cancers and often stain under the microscope for a marker called p53. They can be associated with endome-trial intraepithelial neoplasia, also called EIN, which is thought to be a precursor lesion for uterine serous papillary carcinoma.