Primary renal tumors are uncommon in dogs with prevalence rate of approximately 1%. Renal carcino-ma originating from epithelium of proximal convoluted tubules are more likely to be affected to Middle-aged dogs (average age, 8y), males about twice as often as bitches. A 10-year-old, female, German Shepherd dog with history of anorexia, vomitting and hematuria was referred to the Animal Disease Diagnostic Division in Animal and Plant Quarantine Agency. The dog was necropsied and sev-eral organs were collected, fixed in 10% phosphate-buffered formalin, embedded in paraffin wax and sectioned for histopathology. Grossly, the kidneys were bilaterally enlarged (18×12×8 cm; left, 18×10×8 cm; right). The numerous cysts varying sizes from 3 to 6 cm in diameter were protruding from the surface of both kidney. A large nodule (10×6×6 cm) was discovered between cardiac and diaphragmatic lobe in the right lung. Immunohistochemical examination revealed strong positive reaction to cytokeratin and ki-67 in the nuclei of the epithelial tumor cells. But showed negative reactions to vimentin and CD10. Based on the pathological and immunohistochemical examination, we diagnosed as the bilateral renal cystadenocarcinoma in German shepherd dog.
