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: Medicine
All of the following statements regarding primary effusion lymphoma are true, except: 
Select and explain. 
A. It generally presents in elderly patients, B. There is often an association with HHV-8, C. The proliferating cells are NK cells, D. Patients are commonly HIV positive
C: The proliferating cells are NK cells
Answer: C: The proliferating cells are NK cells 
Explanation: Primary effusion lymphoma is an aggressive B cell lymphoma. The proliferating cells are B cells and not NK cells. All other features mentioned above are associated with primary effusion lymphoma. Ref: Harrison's Principles of Internal Medicine, 16th Edition, Pages 1121-22.