RESUMEN
Desmoplastic fibroma (DF) is a benign yet locally aggressive intraosseous tumour rarely encountered in the mandible. It often mimics other oral lesions. Familial adenomatous polyposis (FAP) is a condition in which individuals tend to develop multiple colorectal polyps, which may convert to colorectal cancer unless treated. FAP has various colonic and extra-colonic manifestations, including oral manifestations. A case of DF of the mandible in a 5-year-old child is presented here. The patient remained free of recurrence 4 years after segmental resection and immediate reconstruction with a fibula free flap. Subsequent genetic testing revealed FAP, implicating DF as an early oral manifestation. A review of the existing literature emphasizes the challenges in diagnosing DF and its association with FAP, stressing the importance of comprehensive assessment and genetic screening in suspected cases.