This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti-Neoplastic Agents, Subject name: Pharmacology
A 40 year old lady with breast cancer has undergone MRM and is on Tamoxifen for 1 year. She now has presents with bleeding per vaginum 4-5 times. What is the probable cause: 
Select and explain. 
A. Bleeding disorder, B. Endometrial cancer, C. Ovarian cancer, D. Cervical cancer
B: Endometrial cancer
Answer: B: Endometrial cancer 
Explanation: Ans. (b) Endometrial cancerRef: KDT 6th ed. / 304-5* Tamoxifen is selective estrogen receptor modulator (SERM).* It is having agonistic activity at uterine endometrium.Action of TamoxifenAgonistic activityAntagonistic activityUterus: causes proliferation of endometrium - can cause vaginal bleeding as seen in the caseBreast CABone: decrease resorptionBlood vesselsLipid profile: decrease LDL without affecting HDL ->> decrease risk of CAD