Reactive plasmacytosis and lymphocytosis in acute myeloid leukemia

The association of plasmacytosis and lymphocytosis with acute myeloid leukemia (AML) has been documented in isolated case reports. We examined 149 cases (134 adults, 15 children) of newly diagnosed AML and found 9 adults (6%) with > or = 5% plasma cells and 1 child and 1 adult with > or = 20% lymphocytes. Lymphocytes constituted 25% and 42% of marrow cellularity in the adult and child respectively and persisted throughout remission in the child's marrow. The percentage of morphologically normal plasma cells ranged from 5% to 13% (mean 7%). Monoclonal immunoglobulins were not detected with immunostaining or flow cytometry. Hypergammaglobulinemia was present in 3 cases, and a monoclonal increase in IgG-kappa in 1. Plasmacytosis was not seen in remission marrows from these patients (n = 4). Lymphocytosis or plasmacytosis occurs in approximately 7% of patients with AML, appears reactive in nature, and may represent an immunological response to tumor. Monoclonal paraproteins may occur without other evidence of B-cell neoplasia.