A 58-year-old woman comes to the physician because of intermittent vaginal bleeding during the past 3 months. She has been treated with tamoxifen since having a partial mastectomy and radiation therapy for a stage II carcinoma of the left breast 4 years ago. Her last menstrual period was at the age of 48 years. She has never had an abnormal Pap smear. Speculum examination shows no abnormalities. Bimanual examination shows no abnormal masses. Which of the following structures is the most likely source of the bleeding?
A. Cervical canal
B. Fallopian tube
D. Uterine endometrium
Correct answer : D. Uterine endometrium
History of tamoxifen intake and the complaint of post menopausal bleeding suggests the diagnosis of endometrial carcinoma.Normal pap smear and speculum examination helps rule out cervical cancer.
Tamoxifen is a selective estrogen receptor modulator (SERM). It acts as an estrogen receptor antagonist in the breast tissue and a partial agonist in the endometrial tissue. It increases the risk for endometrial carcinoma.