This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hematology, Subject name: Pathology
[{'content': 'A 55-year-old man complains of pain in his back, fatigue and occasional confusion. He admits to polyuria and polydipsia. An X-ray examination reveals numerous lytic lesions in the lumbar veebral bodies. Laboratory studies disclose hypoalbuminemia, mild anemia, and thrombocytopenia. A monoclonal IgG peak is demonstrated by serum electrophoresis. Urinalysis shows 4+ proteinuria. A bone marrow biopsy discloses foci of plasma cells, which account for 18% of all hematopoietic cells. What is the appropriate diagnosis? \nSelect and explain. \nA. Acute lymphoblastic lymphoma, B. Chronic lymphocytic leukemia, C. Extramedullary plasmacytoma, D. Multiple myeloma', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Plasma cell myeloma (multiple myeloma) is characterized by a multifocal infiltration of malignant plasma cells in the bone marrow. Major diagnostic criteria for plasma cell myeloma include marrow plasmacytosis (>30%), plasmacytoma on biopsy, and immunoglobulin paraprotein (M-component). In this patient, the neoplastic clone secretes excess kappa light chains. Waldenstrom macroglobulinemia is a neoplastic disorder of small lymphocytes that secrete IgM.Diagnosis: Multiple myeloma', 'role': 'assistant'}]