In vivo confocal microscopic features of canine primary corneal squamous cell carcinoma.

Objective: To describe the in vivo confocal microscopy (IVCM) findings in dogs with primary corneal squamous cell carcinoma (SCC).

Animals: Eight dogs with primary corneal SCC.

Procedures: Dogs diagnosed with primary corneal SCC by histopathology were examined with a modified Heidelberg Retina tomograph and Rostock Cornea Module prior to surgical intervention. The findings from the IVCM examination were correlated with clinical details from ophthalmic examinations and diagnostic test results.

Results: Eight eyes from eight dogs with unilateral primary corneal SCC were examined. Corneal lesions were characterized with IVCM by abnormal epithelial cells that were polygonal and enlarged with marked morphological variability and anisocytosis within individual corneas. The abnormal cells displayed variable reflectivity, but most had highly reflective cellular borders and moderately reflective cytoplasm. Cells that were markedly and diffusely hyperreflective were also occasionally observed possibly representing keratinization and dyskeratosis. On IVCM, neoplastic cells were grouped into cords, clusters, and sheets, and nests of neoplastic cells often invaded the underlying corneal stroma. Keratin pearls were a frequent finding and appeared as circular whirls of neoplastic epithelial cells arranged around concentric layers of hyperreflective amorphous material within a dark cyst-like space. Abundant blood vessels and scattered leukocytes were present in all tumors. There was a high degree of morphologic agreement between IVCM analysis and histopathological findings in all cases.

Conclusions: The distinguishing features of primary corneal SCC during IVCM examine were similar to those seen in histopathologic examination of tumor sections, including enlarged and pleomorphic squamous epithelial cells, anisocytosis, keratin pearl formation, and dense vascularization.