Auer Rod–Like Inclusions in Myeloma Plasma Cells With Aberrant CD34, CD117, and CD33 Expression

PresentationA 73-year-old man presented with acute kidney injury and elevated ferritin (1620 ng/mL).Laboratory investigations showed markedly elevated serum κ free light chains (8948 mg/L; κ/ λ ratio, 1420), with otherwise normal blood counts, calcium, and serum protein electrophoresis.Imaging demonstrated no lytic bone lesions. Key Learning Points• Auer rod-like inclusions can occur rarely in plasma-cell neoplasms.• These inclusions do not establish myeloid lineage.• Aberrant CD34, CD117, and CD33 expression may accentuate resemblance to myeloblasts.• Integrated morphological and flow-cytometric assessment can prevent misclassification as a myeloid malignancy. ConclusionRecognition of this rare morphological-immunophenotypic overlap is important for distinguishing plasmablastic myeloma from an acute myeloid neoplasm.