Presumed myxosarcoma in the eyelid of a cat: Case report.

Objective: To describe the clinical and pathological characteristics of a neoformation suggestive of myxosarcoma in a cat's eyelid.

Animal studied: An 11-year-old mixed-breed castrated female cat presented with a nodule on the lower eyelid approximately 1.6 cm in diameter, multilobulated, non-ulcerated, soft, and adhered to both the skin and conjunctiva of the lower eyelid.

Procedures: The incisional biopsy revealed findings suggestive of a peripheral nerve sheath tumor. After performing an exenteration of the right eyeball to ensure a safe surgical margin, the tissue samples were sent for histopathological analysis and later for immunohistochemistry.

Results: Microscopic evaluation classified the mass as a grade-I mesenchymal neoplasm, suggesting myxosarcoma and malignant peripheral nerve sheath tumor as differential diagnoses. An immunohistochemical examination was carried out to differentiate the neoplasm. Once tumors of neural origin were excluded, the diagnosis of myxosarcoma was indicated as the most likely.

Conclusion: We report a presumed case of eyelid myxosarcoma in a cat, highlighting its relevance in the differential diagnosis in the evaluation of eyelid and conjunctival neoplasms in cats.