Synchronous Odontogenic Fibromyxoma and Compact Osteoma in a Pediatric Patient: A Rare Case Report Mimicking Ameloblastic Fibro-Odontoma

Odontogenic myxoma is a rare, benign mesenchymal odontogenic neoplasm. Microscopically, odontogenic myxoma consists of spindle-shaped or stellate cells within an myxoid stroma. In rare tumors, the stroma contains heavy collagen deposition, and they are then termed odontogenic fibromyxomas. We report an unusual synchronous presentation of an odontogenic fibromyxoma and an osteoma in a 12-year-old boy, which clinically mimicked an ameloblastic fibro-odontoma. The patient presented with a left mandibular mass. Imaging revealed an extensive 51-mm osteolytic lesion accompanied by a hyperdense calcified mass. Radiographic findings were suggestive of an ameloblastic fibro-odontoma. A biopsy of the tumor was performed, and the calcified mass was excised. Histopathological analysis confirmed the diagnosis of an odontogenic fibromyxoma with an associated compact osteoma. The patient underwent a partial mandibular resection and remains disease-free at the 12-month follow-up. A synchronous occurrence of an odontogenic myxoma and an osteoma is rare and can mimic other lesions, making diagnosis challenging.