Abstract
We report here a rare case of malignant myoepithelioma occurring in the maxilla, accompanied by extensive osteoid formation. The patient was a 20-year-old Japanese man with a rapidly swelling mass in the hard palate. Expressions of bone sialoprotein (BSP) and osteopontin (OPN) were examined by immunohistochemistry, in situ hybridization (ISH) and RT-PCR. The mass showed invasive growth of atypical spindle and polygonal cells with abundant osteoid tissue in the stroma. These cells retained immunohistochemical features of myoepithelium, characterized by positive reactivity for cytokeratin (WS), cytokeratin 14, S-100 protein, vimentin, smooth muscle myosin heavy chain and calponin. In addition, malignant myoepithelium noted in and around the osteoid tissue showed expression of BSP on immunohistochemical analysis and ISH, but with no expression of OPN. The normal salivary gland tissue was negative for BSP and OPN. These results suggested that BSP might play a significant role in osteoid development in the present case.
