We report a case of ameloblastic fibro-odontoma (AFO) in the mandibular molar region. A Japanese boy aged 6 years 8 months visited the Pediatric Dentistry Clinic of Osaka University Dental Hospital with dental caries as the chief complaint. Radiography revealed a well-defined homogenous mixed radiopaque mass like dentition above the crown of the mandibular left first molar. At the age of 6 years 9 months, enucleation of the tumor mass was performed under local anesthesia. Based on the histological findings, the diagnosis was AFO. Following enucleation, the left first molar showed a tendency for eruption.
Ameloblastic fibro-odontoma (AFO) is a benign, mixed odontogenic tumor that commonly occurs in the first and second decades of life, with no significant gender inclination and usually found in a posterior area rather than anterior area . Clinically, this tumor is generally characterized as a painless swelling and slow growing mass with delayed tooth eruption . Radiography findings show a well-defined radiolucent area containing various amounts of radiopaque material of irregular size and form . Histologically, the tumor is composed of soft and hard tissues, with the soft tissue component is composed of epithelial strands and small islands of odontogenic epithelium, and the hard tissue component is composed of enamel and dentin . Differential diagnosis of an AFO includes odontoma and ameloblastic fibroma . AFO represents less than 3% of all odontogenic tumours , and approximately 1% among Japanese individuals . Furthermore, there is little potential for recurrence of AFO . Here, we present details of a rare case of AFO in the mandibular molar in a Japanese boy.
A Japanese boy aged 6 years 8 months visited the Pediatric Dentistry Clinic of Osaka University Dental Hospital with dental caries as the chief complaint. Panoramic radiography performed for investigation of caries incidentally revealed a radiopaque lesion in the area of the left first mandibular molar as well as a congenital defect of the left second mandibular molar ( Fig. 2 ). Thereafter, cone-beam computed tomography (CBCT) was performed, which showed various amounts of radiopaque material of irregular size and form within a well-defined radiolucent area ( Fig. 3 ). The degree of completion of root formation of the unerupted first molar was approximately 30% and the lesion had displaced the tooth in an inferior direction. Intraoral examination findings included dental caries in the primary molars and no eruption of the first molars, though no diffuse swelling in the gingiva distal of the left primary first molar was noted ( Fig. 1 ). An extraoral examination also revealed no obvious abnormality such as swelling or facial asymmetry. There was no history of paresthesia or pain, and medical, social, and family histories were unremarkable. We initially suspected a complex odontoma in the molar area of the left mandible.
At the age of 6 years 9 months, under local anesthesia, a gingivectomy was performed for clearing with a radio knife, followed by enucleation of the lesion and fenestration without bone elimination. A tooth-like calcified mass approximately 15 mm in diameter was removed. After enucleation, the wound was kept open to induce eruption of the left first molar.
The resected specimen was examined with hematoxylin and eosin (H-E) staining ( Fig. 4 ). Microscopic findings revealed that half of the resected specimen was occupied by the hard tissue composed of enamel, dentin, and cementum arranged in a disorderly manner. The hard tissue was surrounded by the sparse mesenchymal fibrous tissue like dentin papilla. In the mesenchymal tissue, epithelial islands, as well as alveolar tissue like enamel organ and dental lamina were noted. The tumor was finally diagnosed as an AFO.