A case of zymbal gland carcinoma complicated with leukemia in Wistar rat

A one year old breeder male Wistar rat showed hard mass of 2×5×3 cm size on the right external ear canal and right side of the head. On cut surface, it comprised mainly of a yellowish friable material with occasional cystic spaces. Liver and spleen were enlarged. Microscopically, the neoplasm comprised polygonal cells arranged in islands and trabeculae supported by a fine to moderate fibrovascular stroma. Neoplastic islands and trabeculae form a peripheral layer of flattened to cuboidal epithelial cells with scanty amounts of eosinophilic, granular cytoplasm; round to oval nuclei with finely stippled chromatin and up to 4 distinct nucleoli (basaloid reserve cells); and a central area containing polygonal cells with abundant microvacuolated cytoplasm and round nuclei (sebaceous differentiation). Nuclei were round with finely stippled chromatin and one to two nucleoli. On microscopic examination, liver revealed centrilobular hepatocellular degeneration and infiltration of tumor cells in the sinusoidal and periportal areas while examination of spleen showed diffuse infiltration of round to oval neoplastic cells. It was diagnosed as a rare case of zymbal gland carcinoma complicated with leukemic changes in liver and spleen.