Familial gigantiform cementoma (FGC) is a rare autosomal dominant tumor that is benign but can result in disfigurement of the facial skeleton. Onset of symptoms usually occurs in adolescence, with rapid growth causing expansion of the maxilla and mandible, resulting in significant facial deformity and malocclusion. Radiologic examination defines 3 stages of the lesions: osteolytic, with well-defined radiolucent areas; cementoblastic, in which cementum is formed within the fibrous tissue, represented by radiopacities within the radiolucent zones; and mature, in which the fibrous tissue is almost completely replaced by cementum, represented by a large radioopaque area surrounded by a radiolucent space separating the tumor from normal bone. Histologic examination shows confluent sclerotic avascular cementum, with distinct areas of lamellar bone in some cases. Examination under polarized light reveals a varied birefringent pattern typical of cementum (summary by Finical et al., 1999). Affected individuals may develop osteopenia and sustain long bone fractures after minor trauma (Moshref et al., 2008; Wang et al., 2015). [from
OMIM]