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A 67-year-old man was diagnosed with t(11;14)-positive nonsecretory multiple myeloma. Hematoxylin and eosin staining (panel A, 40× objective, 20 μm scale bar) reveals multiple neoplastic plasma cells harboring intranuclear pseudo-Dutcher bodies (black arrows). Immunohistochemistry (panels B-C, 40× objective, 20 μm) demonstrates absent expression of both κ and λ light chains in these cells. Periodic acid-Schiff (PAS) staining (panel D, 40× objective, 20 μm) shows pseudo-Dutcher bodies are PAS-negative (black arrows), with adjacent neutrophils serving as an internal positive control (white arrows). Flow cytometry (panel E) reveals 99.58% of gated CD138⁺ plasma cells exhibit a cytoplasmic κ/λ double-negative phenotype. Immunofixation electrophoresis (panel F) of sorted CD138⁺ cell lysates detects only an albumin band, with no immunoglobulin bands. Fluorescence in situ hybridization analysis (panel G) confirms the t(11;14) CCND1::IGH translocation. MALDI-TOF (matrix-assisted laser desorption/ionization time-of-flight) mass spectrometry (panel H) identifies a dominant peak at m/z ≈ 66 442, matching human serum albumin, with no immunoglobulin peaks, definitively confirming the inclusions are albumin-derived. These pseudo-Dutcher bodies likely reflect aberrant albumin macropinocytosis.

This case highlights that Dutcher body–like morphology is not pathognomonic for immunoglobulin synthesis.

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