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: Social & Preventive Medicine
M.C. retroperitoneal tumour is - 
Select and explain. 
A. Fibrosarcoma, B. Liposarcoma, C. Dermoid cyst, D. Rhabdosarcoma
B: Liposarcoma
Answer: B: Liposarcoma 
Explanation: Ans is 'b' ie Liposarcoma The most common primary malignancy of the retroperitoneum is sarcoma.(Ref Sabiston) "In the retroperitoneal location, well-differentiated and dedifferentiated liposarcoma and leiomyosarcoma are the most common histiotypes, whereas in the visceral location, GISTs are found most commonly."- Devita's Oncology