Congenital ossifying fibroma (osteofibrous dysplasia) of the tibia--a case report.

Ossifying fibromas of the long bones of the leg are benign lesions occurring in the pediatric age group identical in histological appearance to the similarly named tumor of the jaw in adults. Most frequently presentation occurs after minor trauma with symptoms of a swelling of the tibia or fibula which may be painful. Pathological fracture or limp are also occasional presentations. Congenital cases are extremely rare. We describe an otherwise normal male neonate who presented at birth with a bowed right lower leg. The limb was 1 cm shorter than the other side, with tibia vara and a firm mass situated anteriorly. X-ray showed a mixed lytic and sclerotic lesion in the proximal metaphysis of the tibia. Biopsy showed collagenous stroma containing spindle cells and irregular trabeculae of woven bone rimmed by plump osteoblasts. As the appearances were typical of an ossifying fibroma (osteofibrous dysplasia) no surgical treatment was given. The patient was well with no growth of the tumor and with radiological evidence of healing at 1 year follow up. This case is presented to draw attention to the clinicopathological features of this unusual lesion which must be considered in the differential diagnosis of congenital lesions of the tibia.