Theerachai KosanwatSopee PoomsawatRachai JuengsomjitMahidol University2020-01-272020-01-272019-02-01Journal of Oral and Maxillofacial Pathology. Vol.23, No.4 (2019), S58-S621998393X0973029X2-s2.0-85062211380https://repository.li.mahidol.ac.th/handle/20.500.14594/51878© 2019 Journal of Oral and Maxillofacial Pathology. Ameloblastic carcinoma (AC) is a rare malignant odontogenic tumor. Approximately 138 cases were reported. The majority of these cases occurred in the mandible. Only 57 cases were located in the maxilla. Most of AC cases occur in a primary type. Little is known about AC secondary type (dedifferentiated) since only six cases have been reported. All of previous six cases occurred in the mandible. Here, we presented the first case of maxillary AC secondary type (dedifferentiated) in a 46-year-old female. The first excisional biopsy was diagnosed as basal cell ameloblastoma. Then, the patient underwent partial maxillectomy. A recurrence occurred 17 months later. At this time, tumor cells with cytological atypia were clearly detected. A diagnosis of AC was rendered. Two years later, the patient suffered from another recurrence and received a wide excision with a diagnosis of AC. We considered our case as AC secondary type (dedifferentiated). We discussed the histopathological findings that may be helpful in making a diagnosis of AC. In addition, we consider that the basaloid pattern may be related to malignant transformation in ameloblastoma.Mahidol UniversityMedicineArticleSCOPUS10.4103/jomfp.JOMFP_116_17