Nodular Keratitis Associated With a Previous Diagnosis of Chronic Superficial Keratitis in a German Shepherd Dog: A First Case Report.

Objective: To describe the clinical and morphological features of a case of superficial nodular keratitis in a dog.

Case Description: A German shepherd dog previously diagnosed with chronic superficial keratitis (CSK) presented with a nonpainful, unilateral corneal nodule. After a complete ophthalmic examination, topical treatment with dexamethasone (0.1% dexamethason, WZW) was prescribed. However, the patient did not respond to this treatment; thus, a superficial keratectomy was performed. The lesion was examined histologically and immunohistochemically.

Results: The ophthalmic examination revealed a round, pink, solid nodule, approximately 0.5 cm in diameter, located in the ventral, paracentral cornea. Results from the Schirmer tear test I, tonometry, and fluorescein staining were in the normal ranges. A small amount of mucous discharge and moderate hyperemia of the bulbar conjunctiva were present. The histological examination revealed a solid mass in the superficial corneal stroma under the corneal epithelium. Hematoxylin and eosin (HE) staining showed that the mass was supplied with blood vessels; HE and immunohistochemistry revealed it consisted of a mixture of plasma cells (MUM cells), B lymphocytes (CD79, CD20 cells), T lymphocytes (CD3), and macrophages (Iba1 cells). Mitotic figures were absent. Some nuclei in inflammatory infiltrates displayed a Ki76 reaction. Inflammatory infiltrates were present in the superficial stroma and the corneal epithelium.

Conclusion: These novel results demonstrate that the features of nodular keratitis in a German shepherd dog previously diagnosed with CSK differ from the features of xanthogranulomas, nodular episcleritis, corneal granulomas, pyogranulomatous keratitis, corneal epithelial inclusion cysts, protozoal keratitis, and corneal squamous cell carcinoma.