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
In a patient diagnosed to have choriocarcinoma which is the most common site of metastasis? 
Select and explain. 
A. Liver, B. Lungs, C. Brain, D. Ovaries
B: Lungs
Answer: B: Lungs 
Explanation: Lungs are the most common site of metastasis (75%) followed by vagina (50%). The vulva, kidneys, liver, ovaries, brain, and bowel also may contain metastases. Metastases often develop early and are generally blood-borne because of the affinity of trophoblastic cells for blood vessels.