Ameloblastoma, calcifying epithelial odontogenic tumor, and glandular odontogenic cyst show a distinctive immunophenotype with some myoepithelial antigen expression

Background: Odontogenic neoplasms have some morphologic overlap with salivary gland neoplasms, many of which show myoepithelial differentiation. In the 1980s, an ultrastructural study identified a population of myoepithelial-like cells in calcifying epithelial odontogenic tumor. Myoepithelial derived tumors have since been shown to have distinct immunohistochemical profiles. Methods: We examined a series of odontogenic neoplasms, including 11 ameloblastomas, four calcifying epithelial odontogenic tumors, five glandular odontogenic cysts (GOCs), and five keratocystic odontogenic tumors with a panel of myoepithelial-associated immunohistochemical stains. We also assessed representative control examples of oral mucosa, odontogenic rests, and dentigerous cysts. Results: All of the neoplastic and non-neoplastic oral epithelium-derived entities share a p63-positive, high molecular weight cytokeratin (CK5/6)-positive immunophenotype. Calponin reactivity was at least focally present in two of four calcifying epithelial odontogenic tumors, three of five GOCs, and 10 of 11 ameloblastomas; the sole completely non-reactive ameloblastoma represents a lung metastasis. One case of calcifying epithelial odontogenic tumor was focally positive for glial fibrillary acidic protein. However, other more definitive markers of myoepithelial differentiation, including S-100 and smooth muscle actin, were negative. Two of three calcifying epithelial odontogenic tumors and five of five GOCs were also positive for a low molecular weight cytokeratin (CK7). Conclusions: Ameloblastomas, GOCs, and calcifying epithelial odontogenic tumors show a distinctive immunophenotype which overlaps with that of myoepithelial-derived salivary gland neoplasms but does not provide definitive support for myoepithelial differentiation.