Auer rod-like inclusions in circulating lymphoma cells

Circulating malignant lymphocytes from a 55-year-old woman with small cleaved follicular center cell lymphoma contained azurophilic splinter-shaped cytoplasmic inclusions. By light microscopic and ultrastructural criteria, these structures closely resembled Auer rods found in acute myeloid leukemia; however, the authors could not find cytochemical evidence of lysosomal origin (results were negative for myeloperoxidase, Sudan black B, acid phosphatase, and periodic acid-Schiff). Immunostaining and flow cytometric analysis confirmed a monoclonal IgM-kappa immunophenotype of the circulating malignant lymphoid cells. The inclusions did not show specific immunoglobulin staining by light microscopic or electron microscopic immunostaining techniques. The authors conclude that these membrane-bound inclusions probably represent aberrant lysosomes in the malignant cells.