Light micrograph of squamous differentiation (right half) in endometrial carcinoma, endometrioid type, Grade 1. 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 womb) 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.