Auer rod-like inclusions in the cytoplasm of B-cell lymphoma cells with bone marrow infiltration

Abstract Auer rod-like inclusions are rarely seen in B-cell neoplasms patients. Here, we present a case of B-cell lymphoma with Auer rod-like inclusions in lymphoma cells. By light and transmission electron microscopy, these structures closely resembled Auer rods which were found in acute myeloid leukemia. The Auer rod-like inclusions were negative for cytochemical staining of myeloperoxidase (MPO), alpha - naphthyl acetate esterase (α-NAE), and periodic acid- schiff (PAS). Immunostaining and flow cytometric analysis confirmed monoclonal Kappa-positive malignant lymphocytes. Interestingly, the Auer rod-like inclusions showed diverse ultrastructural features, which ranged from fusiform, needle-shape, round, crystalline cuboid, long rod, short rod, to others; some were membrane structures, some membrane-free dense structures, and some lamellar structures. The patient was diagnosed with B-cell lymphoma with bone marrow infiltration.