[De novo salivary malignant myoepithelioma: pathologic diagnosis of 19 cases].

OBJECTIVE: To study the pathological characteristics of salivary malignant myoepithelioma with characteristic multinodular architecture. METHODS: To observe the histologic and cytologic characteristics of 19 cases of de novo salivary malignant myoepithelioma with multinodular growth pattern. Immunohistochemistry of calponin, SMA, S-100, GFAP, cytokeratin, PCNA was done on 11 cases and ultrastructure was observed on 3 cases. RESULTS: 19 tumors presented characteristic multinodular growth pattern, mostly accompanied by central necrosis. Neoplastic nests invaded the surrounding normal tissue and tumor cells displayed a variety of pleomorphism. Epitheliod cell was the most predominant cell type. Tumor-related extracellular matrix formation was revealed among tumor cells. Immunohistochemical staining demonstrated that the tumor cells were positive for calponin, SMA, S-100, GFAP, AE1/AE3, CKH and PCNA. Myofilaments were found in neoplastic cell cytoplasm under the electron microscope. CONCLUSION: Histologic and cytologic observation, immunostaining and ultrastructural study all supported the myoepithelial and malignant nature of the tumor.