Auer rod-like inclusions in multiple myeloma

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.