Plasma cell myeloma producing IgG, IgM, and IgA immunoglobulins in a cow

Area of Science:

• Veterinary Pathology
• Oncology
• Immunology

Background:

• Plasma cell myeloma is a rare malignancy of terminally differentiated B lymphocytes (plasma cells).
• This case investigates a rare occurrence of plasma cell myeloma in a bovine patient.

Observation:

• A 6-year-old Holstein cow presented with persistent epistaxis, progressive weight loss, and hyperglobulinemia.
• Necropsy revealed enlarged caudal mesenteric lymph nodes, with neoplastic plasma cell infiltration observed in lymph nodes, spleen, bone marrow, and kidneys.
• Amyloid-like material, Congo red-negative in lymph nodes and Congo red-positive in spleen, kidneys, liver, and adrenal glands, was detected.

Findings:

• Immunohistochemistry confirmed neoplastic plasma cells expressed lambda light chains and three heavy chain classes, but not kappa light chains.
• Nonamyloid deposits stained positive for lambda light chains and heavy chains.
• Plasmacytoid cells positive for IgG, IgM, or IgA were present within the lesions, suggesting potential immunoglobulin class switching.

Implications:

• This case highlights the potential for plasma cell myeloma to manifest with diverse clinical signs and pathological findings in cattle.
• The presence of both amyloid and nonamyloid deposits, along with multi-immunoglobulin expression, provides insights into the complex pathophysiology of bovine myeloma.
• Understanding these mechanisms can aid in the diagnosis and management of similar cases in veterinary oncology.