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A 17-year-old female tiger (Panthera tigris altica) was found dead after suffering from continuously growing mass at the right mammary gland area. At necropsy, a firm tan mass apporximately 25 ㎝ in diameter was noted at the ventral abdomen. The mass was not fixed to the adjacent tissue and mottled tan to red on cut sections. Chains of similar nodules ranging from 2 to 5 ㎝ in diameter were also present along the right mammary glands region. Histologically, the neoplastic masses consisted of lobules that were filled with pleomorphic neoplastic cells and separated by fibrious conntective tissue. The neoplastic cells have hyperchromatic nuclei with prominent nucleolus and moderate amount of cytoplasm. The degree of mitosis was high. Multiple areas of necrosis, hemorrhage, mineralization and tumor emboli were also noted. Metastasis to the regional lymph nodes, lung, liver, spleen, kidney, and adrenal gland were observed. Based on the gross and histopathologic examinations, a diagnosis of lobular type metastatic mammary gland carcinoma was made.
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