Metastatic malignant ameloblastoma of the kidneys.

Ameloblastoma is an uncommon disease in the urological field. The resulting tumors or cysts are of odontogenic epithelial origin, are usually benign in nature and rarely metastasize to distant organs. We describe a case of metastatic ameloblastic carcinoma in both kidneys of a 38-year-old Japanese man, who had a history of malignant ameloblastoma and was referred to us for evaluation because of gross hematuria and left flank pain. Computed tomography showed irregular cystic masses in both kidneys. After we confirmed that the primary lesion and the lung metastatic lesion had not recurred, we treated the patient surgically. Approximately 4 months postoperatively the patient suffered a local recurrence of tumors that was very invasive and aggressive. The patient died 2 months later and the autopsy showed local metastasis only, without any metastatic lesion in the lungs or other organs. The present case showed that malignant ameloblastoma is highly aggressive, and in the case of metastases the prognosis is usually extremely poor.