This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Long-term tamoxifen therapy may cause: 
Select and explain. 
A. Endometrium Ca, B. Ovary Ca, C. Cervix Ca, D. Vagina Ca
A: Endometrium Ca
Answer: A: Endometrium Ca 
Explanation: Long-term tamoxifen therapy is a predisposing factor for endometrial hyperplasia and cancers.
Malignancies caused by Long-term tamoxifen therapy:

Carcinoma endometrium-it is the most common carcinoma associated with it.
Uterine sarcoma.
Rarely liver cancer with a long-term high dose.

Non-malignant effects of tamoxifen on uterus:

Endometrial hyperplasia
Endometriosis
Fibroid uterus
Ovarian cysts
Menstrual irregularities or amenorrhea.