[Effective Treatment of Ameloblastoma in an Odontogenic Cyst with Fenestration before Curative Surgery-A Case Report].

Ameloblastoma is a benign odontogenic tumor that rarely undergoes malignant transformation and metastasis but may be locally invasive and recurrent. Fenestration is used to reduce maxillary odontogenic cysts. Here, we report a case ofameloblastoma that developed in the wall of an odontogenic cyst and was treated with fenestration before curative surgery. A 57-yearold Japanese man presented with a mass on the right side ofthe lower gingiva. Computed tomography revealed a unicystic lesion in the right mandibular body, accompanied by a multicystic area in the right lower canine region. Three involved molars were extracted and the cystic wall was harvested. Biopsy analysis revealed an odontogenic cyst in the unicystic lesion and an ameloblastoma in the multicystic area. The ameloblastoma was thought to have developed in the odontogenic cyst wall. The biopsy wound was maintained as a fenestration for 3 months and the lesion was reduced. Marginal resection of the mandible with cystectomy was performed to preserve mandibular bone continuity and the mandibular nerve. Although fenestration delayed curative surgery, the large cystic lesion reduction helped to avoid complications after curative surgery.