This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chemotherapy, Subject name: Pharmacology
Long-term use of tamoxifen may cause 
Select and explain. 
A. Endometrial CA, B. Cervical CA, C. Vaginal CA, D. Ovarian CA
A: Endometrial CA
Answer: A: Endometrial CA 
Explanation: Tamoxifen acts as an anti-estrogen in breast tissue, but it acts like an estrogen in the uterus. In women who have gone through menopause, it can cause endometrial hyperplasia, which increases the risk of endometrial cancer.Though the risk of developing endometrial cancer from tamoxifen is low (less than 1% per year).