Primary third eyelid lymphoma with aggressive local behavior in a dog

Area of Science:

• Veterinary Pathology
• Canine Oncology
• Ocular Neoplasms

Background:

• Lymphoma is a common canine hematopoietic neoplasm, but primary third eyelid involvement is rare.
• Marginal zone lymphoma of mucosa-associated lymphoid tissue is the most frequent subtype in this location, typically indolent.

Observation:

• A 10-year-old Poodle presented with a third eyelid nodule, surgically excised but recurred rapidly.
• Recurrence involved extensive orbital tissue infiltration, corneal invasion, and conjunctival involvement.
• The mass exhibited macroscopic and microscopic features of aggressive neoplastic growth.

Findings:

• Histopathology revealed intermediate to large neoplastic lymphocytes with epitheliotropism.
• Immunohistochemistry confirmed a B-cell immunophenotype (PAX5, CD20, CD79a positive; CD3 negative).
• Diagnosis: Primary extranodal B-cell lymphoma of the third eyelid with locally aggressive behavior.

Implications:

• This case underscores the potential for aggressive behavior in rare canine ocular lymphomas.
• Early detection and aggressive management may be crucial for improving outcomes in canine third eyelid lymphoma.
• Further research into canine ocular lymphoma subtypes and treatment protocols is warranted.