Malignant mixed tumor (malignant ameloblastoma and fibrosarcoma) of the maxilla. We present a rare case of carcinosarcoma (malignant ameloblastoma and fibrosarcoma) of the left maxilla that developed in a 63-year-old Japanese man. The tumor recurred repeatedly despite multiple surgical removals, radiotherapy, and chemotherapy and led to progressive cachexia; the patient died after 3.8 years of hospitalization. Histopathologic examination revealed that the recurrent tumor was carcinosarcoma, which had progressed from malignant ameloblastoma with fibroma. An autopsy confirmed the diagnosis of malignant mixed tumor with lung metastasis of malignant ameloblastoma and fibrosarcoma. 