Light micrograph of mucinous differentiation (lower portion with lighter pink glands) in an endometrioid carcinoma (darker glands in the upper portion). Uterine cancer is the most commonly diagnosed invasive cancer of the female genital tract. The vast majority of these arise in the endometrium (lining of the uterus) and are endometrioid subtype. Endometrial cancer mostly affects postmenopausal women. The most common risk factor is prolonged exposure to estrogen. Patients usually present with abnormal uterine bleeding.