This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Plasma Cell Disorders and Multiple myeloma, Subject name: Pathology
Beta-2 microglobulin is used as a tumor marker for which of the following diseases? 
Select and explain. 
A. Multiple myeloma, B. Acute lymphoblastic leukemia, C. Hairy cell leukemia, D. Lymphoplasmacytic lymphoma
A: Multiple myeloma
Answer: A: Multiple myeloma 
Explanation: Tumor marker for multiple myeloma is Serum beta-2 microglobulin Serum beta-2 microglobulin level <3.5mg/L indicates better prognosis