Abstract
A six years and four months old Japanese Black cow presented with a solid mass in the left and middle mandible. Treatment involved the administration of antibiotics and the mass was surgically removed. Recurrence of the mass was observed, and the cow exhibited hypersalivation and anorexia before dying naturally. A necropsy revealed a solid subcutaneous mass infiltrating the oral cavity and the left mandibular bone, with hemorrhage and necrosis. Histopathological examination revealed clear, plasmocytic, spindle-shaped, or polygonal neoplastic cells. The neoplastic cells were immunoreactive with cytokeratin, cytokeratin 5, vimentin, smooth muscle actin, and p63. Considering these findings, the mass was diagnosed as malignant myoepithelioma. This is the first report of malignant myoepithelioma arising from the salivary glands in a cow.