<prompt> 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?Acute lymphoblastic lymphomaChronic lymphocytic leukemiaExtramedullary plasmacytomaMultiple myeloma  <response>: 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 