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Neoplastic plasma cells mimic mature neutrophils in plasma cell myeloma with t(11;14)(q13;q32)

Wei Wang and Shimin Hu

A 48-year-old man with a history of diabetes was found to have an elevated serum immunoglobulin G (IgG) level (8.6 g/dL) during a routine blood workup. Further laboratory study and bone marrow biopsy confirmed IgG-κ type plasma cell myeloma. The patient underwent therapy with bortezomib, carfilzomib, and dexamethasone. One year later, he was referred to our hospital for evaluation of stem cell transplant. A bone marrow biopsy was performed. On the core biopsy, there were clusters of cells with bi- to multilobed nuclei, morphologically resembling mature neutrophils (panel A). On smears, these cells are medium- to large-sized, with deeply basophilic cytoplasm, occasional cytoplasmic vacuoles, vague perinuclear hof, and folded or lobulated nuclei (panel B). A monocyte with gray to light-blue cytoplasm was included for comparison (panel B, asterisk). Immunophenotypically, these cells are positive for cyclin D1 (panel C) and CD138 (panel D), with both surface and cytoplasmic κ light-chain expression (panel E). λ light-chain was negative (panel F). Flow cytometric immunophenotyping analysis showed that plasma cells were positive for CD38, CD138, and CD28 (partial), and were negative for CD20, CD45, CD56, and CD117. Conventional cytogenetics revealed 46,XY,der(14)t(11;14)(q13;q32)[6]/46,XY[14], and fluorescence in situ hybridization studies showed IGH/CCND1 rearrangement.

Plasma cell myeloma with t(11;14)(q13;q32) is a distinct subtype of myeloma and tends to have lymphoplasmacytic morphology. Compared with myelomas without this cytogenetic abnormality, it is more often CD20+ and CD56. In the case presented here, the neoplastic plasma cells morphologically resemble mature neutrophils, except for basophilic cytoplasm shown on smears. This anaplastic morphology can cause diagnostic challenges. Future studies to address whether there is an association between this unusual morphology and t(11;14) in plasma cell myeloma will be of interest. The surface light-chain expression described in this case occurs in a small subset of plasma cell myelomas, particularly cases with t(11;14).

Footnotes

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