Acanthomatous ameloblastoma with mucinous glandular differentiation in a dog.

This report describes an atypical case of canine acanthomatous ameloblastoma (CAA) with mucinous glandular differentiation in a 12-year-old male Chihuahua with a right mandibular mass. Initially diagnosed as CAA by biopsy, computed tomography revealed bone lysis, prompting surgical excision. Histological examination showed lobular growth with two distinct neoplastic cell populations: typical CAA-like cells and a minor glandular structure population. Mucinous glandular differentiation in CAA is undocumented in veterinary literature. Immunohistochemistry showed positivity for cytokeratin AE1/AE3 in all tumor cells, and cytokeratin CAM5.2 and Alcian blue staining confirmed glandular cells and mucin. A low mitotic and K-i67 proliferation index suggested low-grade malignancy. This rare case highlights the need for comprehensive histopathological and immunohistochemical analysis to distinguish CAA from other oral tumors.