Endometrial hyperplasia is an overgrowth of endometrial tissue (which is the inner lining of the uterus which shed every month as menstrual blood flow). It is not cancerous. However, there is a form of severe hyperplasia which can be precancerous (especially when there is presence of abnormal cells called atypia). Classification of the hyperplasia includes:
- simple or complex (adenomatous) hyperplasia without atypia, or
- simple or complex (adenomatous) hyperplasia with atypia.
Patients who have endometrial hyperplasia without atypia usually respond well to progestogen therapy and are not at increased risk for uterine cancer. The progression of hyperplasia to endometrial cancer increases as the abnormal cells (atypia) of the hyperplasia develops.