A 68-year-old man has had low back pain over the past 2 months. Laboratory studies show a normochromic, normocytic anemia and azotemia. Serum and urine calcium concentrations are abnormally increased, and urinalysis shows excessive protein (4+) and proteinaceous casts. Bone marrow examination is most likely to show uncontrolled proliferation of which of the following cells?
(A) Basophils
(B) Lymphocytes
(C) Macrophages
(D) Plasma cells
(E) Reticulocytes
(A) Basophils
(B) Lymphocytes
(C) Macrophages
(D) Plasma cells
(E) Reticulocytes