[Benign odontogenic ectomesenchymal tumors]

The group of odontogenic ectomesenchymal tumors consists of odontogenic fibroma (epithelium-rich and epithelium-poor types), odontogenic myxoma, and cementoblastoma. Whereas odontogenic fibromas and cementoblastomas are very rare lesions, odontogenic myxoma is the fourth common odontogenic tumor, preceded only by keratocystic odontogenic tumor, the odontomas, and ameloblastoma. The diagnosis of cementoblastoma rests on its connection to the root of a tooth. The differentiation of odontogenic fibroma and myxoma from other lesions, especially from normal structures such as dental follicles and papillae, may be challenging if the X-ray appearance (localized osteolysis containing a tooth) is not appreciated and subtle histological clues (remainders of inner enamel epithelium at the surface of the lesion, dentin fragments) are not properly recognized. While odontogenic fibromas have almost no tendency for recurrence and are treated by enucleation or local excision, cementoblastomas and especially odontogenic myxomas have a high percentage of recurrence if intralesional procedures are applied. Hence, complete resection with free margins is recommended--at least for larger odontogenic myxomas and, especially, lesions in the maxilla--to prevent further extension to the orbita or base of the skull.