A Rare Case of Gingival Osseous Choristoma Misdiagnosed as Fibroma.

Osseous choristoma is a rare, nonneoplastic lesion defined by the presence of organized lamellar bone within soft tissue. It most frequently affects the dorsal tongue. Gingival involvement is extremely rare, with only nine cases documented in the English-language literature. This report describes a 20-year-old woman who presented with a well-circumscribed, painless, firm, and sessile nodule on the buccal gingiva of the left posterior mandible. Panoramic radiography revealed no pathological alterations. The initial clinical impression was fibroma. Surgical excision was performed. Histopathology revealed well-demarcated nodules of mature lamellar bone within a fibrous stroma, confirming the diagnosis of osseous choristoma. No recurrence was detected at the 6-month follow-up. This case constitutes the tenth reported instance of gingival osseous choristoma. A review of the nine previous cases is also provided to enhance diagnostic precision and clarify clinicopathologic features.