Osteofibrous dysplasia

Osteofibrous dysplasia (OSFD) is a tumor-like bone lesion that usually presents as a painless swelling or anterior bowing of the tibia (Park et al., 1993), although pain may occur in up to 25% of cases and presentation may follow pathologic fracture. Most reports of osteofibrous dysplasia describe isolated tibial lesions, although a significant subgroup describe isolated and ipsilateral fibular involvement. Cases with ulnar and radial involvement have been reported (summary by Hunter and Jarvis, 2002). OSFD is characterized by radiolucent lesions located at the periosteal surface of the diaphyseal cortex, almost exclusively of the tibia and fibula. These lesions are congenital and spontaneously resolve during skeletal maturation; the residuum is most commonly mild bowing at the affected site. Prior to their resolution, secondary complications such as nonunion fractures and pseudoarthrosis formation can occur. Histologically, OSFD lesions exhibit 'zonal architecture' characterized by spindle-shaped fibroblast-like cells in the center of the lesions that are progressively replaced with peripherally located, more differentiated cells from the osteoblastic lineage. The cells lying at the center of the lesions stain for markers of undifferentiated mesenchymal cell states, whereas bridging zones of osteoid with surface osteoblasts and embedded osteocytic cells are interspersed between the lesions. In OSFD, the unossified zones eventually mineralize after replacement with normal osteoid and, finally, bone. This histologic progression corresponds with the clinical and radiographic resolution of the lesions (summary by Gray et al., 2015). Hunter and Jarvis (2002) noted that there may be a relationship between osteofibrous dysplasia and adamantinoma of long bones (102660), although the latter condition usually presents at a later age. [from OMIM]