Large anaplastic spinal B-cell lymphoma in a cat

Area of Science:

• Veterinary Neurology
• Comparative Oncology
• Feline Pathology

Background:

• A 5-year-old domestic shorthair cat presented with tetraparesis, indicating a neurological issue.
• Initial fine needle aspiration cytology suggested malignant round cell neoplasia of possible histiocytic origin.

Observation:

• A left axillary mass was identified, and the neurologic lesion localized to the cervical spinal segment (C1-C6).
• Postmortem examination confirmed an extradural mass at the C1-C2 spinal segment causing spinal cord compression.
• Neoplastic cells infiltrated adjacent vertebral bodies, skeletal muscle, axillary lymph node, and bone marrow.

Findings:

• Immunohistochemistry revealed the tumor cells were CD20+ and CD45R+, consistent with B-cell lymphoma, despite an initial diagnosis of anaplastic sarcoma.
• The feline B-cell lymphoma exhibited unusual features, including marked anisocytosis, anisokaryosis, and the presence of bi- and multinucleated cells.
• PCR testing for antigen receptor gene rearrangement could not confirm clonality of the B-cell population.

Implications:

• This is the first reported case of feline spinal anaplastic B-cell lymphoma with bi- and multinucleated cell morphology.
• The prognostic significance of this specific cell morphology and immunophenotype in feline lymphoma remains undetermined.
• Further research is needed to understand the behavior and treatment of such aggressive feline spinal tumors.