A renal oncocytoma was diagnosed in an 8-year-old female Maltese dog with a history of renal cysts. Tumor cells were not detected until six months after observation of renal cysts. Nephrectomy was performed to treat the neoplasia. Tumor-like masses with numerous nodules were observed in the inner surface of cysts present in the caudal part of the left kidney. Histologically, the tumor consisted of cells with abundant eosinophilic cytoplasm. The diagnosis was based on histological features,

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... dic acid-Schiff reaction, and immunohistochemical cytokeratin staining. Based on a literature review, this is the first canine renal oncocytoma case reported in Korea.