[Malignant ameloblastoma. Apropos of a case].

Ameloblastoma is a locally invasive, histologically nonmalignant tumor that may on very rare occasions give rise to metastases. A patient with a mandibular ameloblastoma presenting typical histologic appearances developed a pulmonary metastasis confirmed by histology as arising from the primary tumor. Two groups of these extremely rare malignant ameloblastomas can be distinguished: those without histologic signs of degeneration that give rise to metastases identical to the primary lesion, and those with degenerative signs provoking metastases with the histologic appearance of undifferentiated carcinoma. No relation appears to exist between size of primary tumor, histologic type of ameloblastoma, or its course and tendency to produce metastases.