RESUMO
Ossifying fibroma is a relatively rare benign primary bone tumor which arises typically within the jaw bones and only rarely affects the long bones. In 1966, Kempson first described ossifying fibroma of the long bones because the lesion has a histologic pattern like the ossifying fibroma of the jaw. This rare lesion resembles monostotic fibrous dysplasia but can be differentiated from it on histologic and clinical grounds. Histologically, ossifying fibroma is characterized by osteoblasts rimming spicules of bone within a fibrous stroma with evidence of lamellar transformation of bone, and clinically by frequent recurrence and aggressive progression of the lesion. Because of its rarity, we present a case of ossifying fibroma which arised in the right tibia of a 34 month old boy.