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Auer rod-like inclusions in multiple myeloma
G Metzgeroth1, W Back, O Maywald
1III. Medizinische Universitätsklinik, Fakultät für Klinische Medizin Mannheim, University of Heidelberg, Wiesbadenerstr. 7-11, 68305 Mannheim, Germany. georgia.metzgeroth@med3.ma.uni-heidelberg.de
Abstract:
We report a case of IgA multiple myeloma, in which the plasma cells showed multiple azurophilic, Auer rod-like intracytoplasmic inclusions in May-Grünwald-Giemsa-stained marrow smears. Cytochemical stainings revealed a strong alpha-N-esterase activity of these inclusions, whereas the reactions for peroxidase, Sudan black, chloroacetate esterase, and PAS were negative. Immunostaining verified IgA-kappa inside the plasma cells. The inclusions, however, were negative. Amyloid and lysozyme were also not detectable. Electron microscopy showed Auer rod-like inclusions with a smooth surface in the neighborhood of a well-developed rough endoplasmic reticulum, but with no direct relation to it. The inclusions showed a fine lamellar substructure, and the periodicity of the filamentous striations was about 10 nm, comparable with the substructure of typical Auer rods. Our findings suggest that the azurophilic inclusions in multiple myeloma are Auer rod-related structures, which likewise consist of active lysosomal enzymes. In contrast to the Auer rods in acute myeloblastic leukemia (AML), however, the inclusions in multiple myeloma consist of typical plasma cell enzymes.
Insights
This study identifies Auer rod-like inclusions in IgA multiple myeloma plasma cells. These inclusions contain lysosomal enzymes, distinguishing them from Auer rods found in acute myeloblastic leukemia.
Area of Science:
- Hematology
- Oncology
- Cell Biology
Background:
- Multiple myeloma is a plasma cell malignancy.
- Auer rods are typically associated with acute myeloid leukemia.
- Intracytoplasmic inclusions in myeloma require further characterization.
Observation:
- Plasma cells in a case of IgA multiple myeloma exhibited azurophilic, Auer rod-like intracytoplasmic inclusions.
- Cytochemical staining showed strong alpha-N-esterase activity in the inclusions, with negative results for peroxidase, Sudan black, chloroacetate esterase, and PAS.
- Immunostaining confirmed IgA-kappa within plasma cells, but not in the inclusions.
Findings:
- Electron microscopy revealed Auer rod-like inclusions with lamellar substructure, similar to typical Auer rods.
- The inclusions demonstrated active lysosomal enzymes, specifically alpha-N-esterase.
- These inclusions, unlike AML Auer rods, were composed of plasma cell-associated enzymes.
Implications:
- The findings suggest these inclusions are Auer rod-related structures specific to multiple myeloma.
- This expands the understanding of morphological variations in plasma cell neoplasms.
- Characterizing these inclusions may aid in the differential diagnosis of plasma cell disorders.
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