An oncologist is discussing multiple myeloma. Which of the following cell types is involved with this neoplasm?

A. Hyperchromic: Hyperchromic erythrocytes have an increased hemoglobin concentration and may appear darker than normal. Red blood cells have a limited ability to become truly hyperchromic, making this finding uncommon. It does not describe cells with reduced hemoglobin content.

B. Hypochromic: Hypochromic erythrocytes contain a decreased concentration of hemoglobin, resulting in a pale appearance with increased central pallor. This finding is commonly associated with disorders of hemoglobin synthesis such as iron deficiency anemia. It directly reflects low hemoglobin concentration within the erythrocytes.

C. Macrocytic: Macrocytic erythrocytes are larger than normal and are typically linked to vitamin B12 or folate deficiency. The defining feature is increased cell size rather than hemoglobin concentration. Macrocytosis does not specifically indicate reduced hemoglobin within the cells.

D. Microcytic: Microcytic erythrocytes are smaller than normal and are often seen in iron deficiency anemia or thalassemia. Although these cells may also be hypochromic, the term refers specifically to decreased cell size. It does not directly describe low hemoglobin concentration.

A. T cells: T lymphocytes are primarily involved in cell-mediated immunity and are implicated in conditions such as lymphomas and certain leukemias. Multiple myeloma does not originate from T-cell lines. The disease process specifically affects antibody-producing cells rather than cell-mediated immune cells.

B. B cells: Multiple myeloma arises from malignant transformation of B lymphocytes that have differentiated into plasma cells. These abnormal cells produce excessive amounts of a single immunoglobulin, leading to characteristic clinical features. The neoplasm is therefore classified as a disorder of the B-cell lineage.

C. Immature plasma cells: Immature plasma cells are more commonly associated with plasma cell leukemia or early precursor disorders. Multiple myeloma involves clonal proliferation of plasma cells that are typically mature rather than immature. The disease reflects abnormal antibody production rather than early cell precursors.

D. Mature red blood cells: Mature red blood cells are responsible for oxygen transport and are not involved in neoplastic immune disorders. While anemia may occur as a complication of multiple myeloma, erythrocytes are not the malignant cell type. They are affected secondarily due to marrow infiltration.