Periocular basal cell carcinoma in a donkey: case report

Area of Science:

• Veterinary Ophthalmology
• Comparative Oncology
• Equine Neoplasia

Background:

• Basal cell neoplasms are uncommon, slow-growing, benign tumors in horses, primarily affecting skin and eyelids.
• Malignant presentations of basal cell neoplasms are exceedingly rare in equids.

Purpose of the Study:

• To report a case of basal cell carcinoma (BCC) in the periocular region of a donkey.
• To describe the clinical, cytological, histopathological, and immunohistochemical findings of this rare equine neoplasm.

Main Methods:

• Ophthalmological examination and mass measurement.
• Cytological evaluation for preliminary diagnosis.
• Surgical globe exenteration.
• Histopathological and immunohistochemical analysis for definitive diagnosis and characterization.

Main Results:

• A 10-year-old donkey presented with a large (3.0 × 2.5 × 1.5 cm) periocular mass adhered to the cornea.
• Cytology suggested a malignant epithelial neoplasm; histopathology confirmed basal cell carcinoma with infiltrative growth.
• Immunohistochemistry was positive for pan-cytokeratin and negative for vimentin, Sox-10, and Melan-A.
• The donkey showed no recurrence or complications 12 months post-exenteration.

Conclusions:

• Basal cell carcinoma, though rare, should be considered in the differential diagnosis of periocular neoplasms in horses and donkeys.
• Surgical globe exenteration can be an effective treatment for periocular BCC in equids, with favorable outcomes.
• This case highlights the importance of thorough diagnostic workup for unusual equine ocular tumors.