Auer rod-like cytoplasmic inclusion bodies in nodal marginal zone lymphoma cells

Abstract

A 58-year-old woman was referred to our hospital because of right axillary lymphadenopathy. A biopsy of the lymph node was performed. The lymph node section showed a diffuse proliferation of moderate-size atypical lymphoid cells with mild irregular-shaped nuclei and pale cytoplasm (Fig. 1). Immunohistochemical staining revealed that the atypical lymphoid cells were positive for CD19, CD20, and CD43, and negative for CD10, CD5, and cyclin D1. Cytogenetic analysis using the conventional G-banding method revealed normal karyotype. By FISH analysis, t(11;14)(q13;q32) was not detected. On the basis of these findings, the patient was diagnosed with nodal marginal zone lymphoma (MZL). No other surface lymph nodes were palpable at physical examination; however, some swollen lymph nodes adjacent to the sternum (Fig. 2a, arrow) were detected on computed tomography. In addition, fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (FDG-PET) revealed abnormal FDG accumulations at the swollen lymph nodes and in the sternum (Fig. 2b, arrows). Examination of bone marrow smears obtained from the sternal site showing FDG accumulation revealed many abnormal lymphoid cells; needleshaped inclusions that were morphologically similar to Auer rods were observed in the cell cytoplasm (Fig. 3a). Because the findings of bone marrow smears taken from the patient’s iliac bone were normal, we judged that these abnormal cells were lymphoma cells arising due to direct invasion to the sternum. Microscopic analysis revealed that the cytoplasmic inclusions had variable shapes. Although most lymphoma cells displayed multiple needle-like or splinter-shaped inclusions in their cytoplasm, some exhibited considerably thick inclusions (Fig. 3b). We did not find these inclusions in the lymph node biopsy specimen, which was prepared by fixing with formaldehyde and