Abstract
BACKGROUND: Ameloblastic fibroma (AF) is a rare benign odontogenic tumor characterized by the coexistence of epithelial and mesenchymal components, typically arising intraosseously in the posterior mandible during the first two decades of life. Its peripheral variant, occurring extraosseously in gingival soft tissue without bone involvement, is exceedingly rare. Owing to its clinical resemblance to reactive gingival lesions, peripheral AF poses diagnostic challenges and is frequently misdiagnosed without histopathological confirmation. CASE PRESENTATION: We report a case of peripheral AF in a 34-year-old Chinese woman who presented with a slow-growing, asymptomatic soft tissue mass on the palatal gingiva between teeth 23 and 24. Clinical examination revealed a well-defined, sessile lesion measuring 6 mm × 6 mm, with no signs of pain, bleeding, or tooth mobility. Radiographic evaluation, including panoramic imaging and cone beam computed tomography, confirmed the absence of bone involvement. The lesion was excised under local anesthesia, followed by root planing and soft tissue reconstruction using a laterally positioned flap to preserve esthetics. Histopathological examination demonstrated classic features of AF, including epithelial strands and cords within a cell-rich ectomesenchymal stroma, with peripheral palisading and central stellate reticulum-like cells. Immunohistochemistry revealed low Ki-67 proliferation index and negative BRAF expression, supporting the benign nature of the lesion. The final diagnosis was peripheral ameloblastic fibroma. Follow-up over 20 months showed no recurrence and excellent gingival healing with preserved architecture. CONCLUSION: This case underscores the importance of considering peripheral AF in the differential diagnosis of gingival masses, particularly those mimicking reactive lesions. Histopathological and immunohistochemical analyses are essential for accurate diagnosis and appropriate management. Conservative surgical excision with careful flap design can achieve excellent functional and esthetic outcomes. Given its rarity, every well-documented case of peripheral AF contributes meaningfully to the understanding of its clinical behavior and optimal treatment strategies.