Precursor B-1 B cell lymphoma in a newborn calf

Area of Science:

• Veterinary Pathology
• Immunology
• Oncology

Background:

• Neoplastic lesions in animals can originate from various cell types, impacting different organ systems.
• Lymphoma classification relies on cell lineage markers and tissue distribution.
• B-1 cells, a distinct B cell subset, have unique developmental and functional characteristics compared to B-2 cells.

Observation:

• A newborn Holstein calf presented with neoplastic lesions in the skin and thoracic/abdominal cavities.
• Tumor cells lacked involvement of bone marrow, spleen, thymus, and most lymph nodes.
• Immunohistochemistry revealed tumor cell positivity for CD79a (B cell marker), CD5 (B-1 cell marker), and terminal deoxynucleotidyl transferase (immature lymphoid precursor marker).

Findings:

• A diagnosis of precursor B-1 B cell lymphoma was established based on immunophenotype and lesion distribution.
• The presence of CD5 and terminal deoxynucleotidyl transferase supported a B-1 cell origin.
• The case was differentiated from typical calf lymphoma, which is of B-2 cell origin, CD5-negative, and involves widespread lymphadenopathy and organ infiltration.

Implications:

• This case expands the understanding of B-1 cell lymphoma in young animals.
• It underscores the importance of specific cell markers for accurate lymphoma subtyping in veterinary oncology.
• The distinct presentation suggests unique oncogenic pathways or developmental origins for precursor B-1 B cell lymphoma in calves.