Malignant ameloblastoma. A case report.

The cytologic features of malignant ameloblastoma, a rare tumor of the jaw, are described. Fine needle aspiration smears showed high cellularity, with small basaloid and polygonal epithelial cells with mild to moderate pleomorphism lying singly or in clusters. In Giemsa-stained smears, pinkish stroma with stellate cells or irregularly shaped nuclei and isolated spindle cells were seen in the background. Histopathology of the tumor showed sheets of cells with features of malignancylike atypical mitosis and vascular invasion. The tumor cells stained positive for keratin on immunohistochemistry. A review of cytology smears revealed that the features were sufficiently characteristic of an ameloblastoma, but it was difficult to label the lesion malignant on fine needle aspiration cytology.