Ossifying Fibroma

     Ossifying fibroma, also known as osteofibrous dysplasia, is a benign fibrous tumor with local aggressive behavior. The most common site in adults is the mandible. The most common site in children is the tibia, followed by other long bones. Ossifying fibroma occurs during the first decade of life and presents clinically as a painless, enlarging mass.
     Ossifying fibroma has a distinctive radiologic picture. This lytic lesion occurs in the anterior cortex of the diaphysis or metaphysis of the tibia and often causes anterior-posterior bowing. This well-circumscribed tumor has a multi-loculated appearance and causes distortion of the thin cortex. Ossifying fibromas have increased uptake on bone scan. The radiologic differential
includes ad amantinoma, fibrous dysplasia, nonossifying fibroma and osteoblastoma.
     Microscopically, ossifying fibroma consists of irregular spicules of trabecular bone lined by osteoblasts. These osteoblasts produce a rim of lamellar bone around centers of woven bone. Ossifying fibroma stains positive for cytokeratin. The question has been raised if ossifying fibroma is a relative of fibrous dysplasia or a true neoplasm. Most recently, it has been surmised
that ossifying fibroma and adamantinoma are on a continuum with osteofibrous dysplasia-like adamantinoma representing an -intermediate step between the two lesions.l
     Treatment of ossifying fibroma in older patients includes conservative curettage. A thorough pathologic examination must be done for the presence of adamantinoma. Patients who still have open growth plates are observed. If bowing of the tibia becomes an issue, bracing is recommended. Ossifying fibroma does not metastasize.

Springfield, DS et al., Relationship Between Osteofibrous Dysplasia and Adamantinoma, Clinical Orthopaedics and Related Research, 309:234-244, December, 1994.

Marks, KE and TW Bauer, Fibrous Tumors of Bone, Orthopedic Clinics of North America, 20(3):377-393, July 1989.

Bulloughs, Peter, Orthopaedic Pathology (third edition), Times Mirror International Limited, London, 1997.

Huvos, Andrew, Bone Tumors: Diagnosis. Treatment and Prognosis, W.B. Saunders, Co., 1991.









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