A peripheral ameloblastic fibro-odontoma in a 3-year-old girl: case report, immunohistochemical analysis, and literature review

Abstract

Ameloblastic fibro-odontoma (AFO) predominantly occurs in the jaw bones of children and young adults. Extraosseous AFO is extremely rare. We describe a peripheral ameloblastic fibro-odontoma in the maxillary gingiva of a 3-year-old girl. The clinical appearance resembled fiery red reactive gingival lesions. The histopathological examination of the excised lesion showed small islands and cords of odontogenic epithelium with cellular myxoid stroma in the subepithelial tissue. The mass contained calcified material and an enamel-like deposit. Many small blood vessels appeared in the connective tissue surrounding the odontogenic epithelium. The immunohistochemical assays showed strong reactivity for amelogenin, β-catenin, CD44, and CD31 in the tissue sections. There was no recurrence after the 1-year follow-up. Because this lesion clinically resembles other nonneoplastic lesions and is very rare in gingiva, establishing a correct diagnosis is achieved only based on specific histological characteristics. Conservative excision of the tumor is the treatment of choice.

Figure 1

Clinical and radiographic appearances. (a) Frontal view: a fiery red gingival lesion on the labial side of the primary maxillary right central incisor. (b) Occlusal view: the maxillary right primary central incisor was a little palatally displaced. (c) A pulpectomy and restoration had been done for the primary maxillary right central incisor at a local dental clinic. There was no observable radiopaque abnormality in the periapical radiograph.

Figure 2

Hematoxylin and eosin staining for the gingival lesion. (a) The black arrow indicates a dental papilla-like tissue. (b) The red arrows denote abundant small blood vessels. (c) A large mineralized matrix appears like enamel or dentin structures. (d) There are several islands of odontogenic epithelium. One of them clearly exhibits enamel organ differentiation. Panels (b), (c), and (d) are magnifications (×4) of the white squares of panel (a). Scale bar = 200 μm for panel (a) and 50 μm for panels (b), (c), and (d).

Figure 3

Clinical appearance 1 year after excisional biopsy for the gingival lesion.

Figure 4

Immunohistochemistry for amelogenin, β-catenin, CD31, and CD44. The stainings showed that amelogenin, β-catenin, and CD44 were strongly expressed in the enamel epithelial cells. Some of the stromal cells, leukocytes, and endothelial cells were also positive for CD44 staining. CD31 staining appeared in the endothelial cells of the tumor stroma, especially in the area adjacent to the enamel epithelium. Scale bar = 100 μm for all panels but the bottom right (25 μm).