ENZYMECYTOCHEMISTRY AND IMMUNOHISTOCHEMISTRY IN MONOCLONAL GAMMOPATHY AND REACTIVE PLASMACYTOSIS

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Abstract
Peripheral blood smears and bone-marrow smears from 29 patients with malignant M-components (25 with multiple myeloma [MM] and 4 with malignant lymphoma), 13 patients with benign monoclonal gammopathy (BMG), and 20 patients with polyclonal reactive plasmacytosis were examined by leukocyte alkaline phosphatase score (LAP-score) and by acid phosphatase score in plasma cells from bone-marrow smears. Marrow biopsy tissue sections from all patients were examined by the 3 layer unlabeled immunoperoxidase technique to detect cytoplasmic Ig. The LAP-score was significantly higher in patients with malignant M-components than in patients with BMG and also higher in IgA and IgG myeloma than in IgA and IgG BMG, but the latter difference was not significant. A significant positive correlation between paraprotein concentration and LAP-score was found in MM. Plasma cell acid phosphatase score showed no clear distinction between multiple myeloma and BMG. Immunohistochemical examination showed a distinct monoclonal pattern in both MM and BMG, allowing identification of the M-component which in all cases corresponded to the M-component detected by serum examination. Cells producing Ig classes not matching the M-component were more rare in MM than in BMG, but the difference between the 2 conditions was quantitative and allowed no clear distinction.