Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Monostotic Fibrous Dysplasia of the Rib
- Radiologic Findings
- Chest PA shows expanded left 9th rib. The cortex of the involved rib remains intact. The bone has ground glass appearance. CT scan with bone setting demonstrates the internal trabeculated configuration and a focally calcified or ossified matrix. Enhanced CT scan shows a well-defined expansile bony mass with mottled appearance. Posterior whole-body image from Tc-99m methylene diphosphonate (MDP) bone scan shows markedly increased radionucleide accumulation of the tumor.
Photomicrograph show poorly cellular fibrous tissue containing numerous trabeculae of non-lamellar bones (woven bone) (Hematoxyline-Eosine stain, x40).
- Brief Review
- Fibrous dysplasia (FD) is the most common benign tumor of ribs. It accounts for 17% to 33% of primary rib lesions other than myeloma. About 5.9% to 19.6% of primary rib lesions other than myeloma. About 5.9% to 19.6% of monostotic FD occurs in the ribs. The second rib is a common site for FD. In most cases, the discovery of FD is an incidental finding. FD occurs anywhere along the shaft of the rib.
Pathologically FD is composed of fibrous tissue containing bone trabeculae. Fibrous stroma is a myxofibrous tissue of low vascularity, while the bone trabeculae are composed of woven bone. Woven bone refers to bone with little layering, while lamellar means bone with well-formed layers.
Radiographically, FD of the rib is a slow-growing, well-marginated osteolytic lesion that is centrally located within the medullary space and usually expands the bone. The cortex may be irregular and thin but remains intact. The margins are sharp and often are sclerotic. Occasionally bone expansion may be asymmetric toward the side thoracic cavity. FD may extend throughout a long segment of rib, being 5cm to 19cm in length. Long lesions of FD may demonstrate variable degrees of expansion throughout. The matrix of this lesion may appear radiolucent or may demonstrate peripheral trabeculations and appear loculated, or it may demonstrate variable degrees of mineralization with a faint amorphous homogeneous increase in density, the so-called ground-glass appearance. Radiographic density of the FD is determined by the amount of woven bone. Trabeculated appearance is due to reinforced subperiosteal bone ridge in the wall of the FD.
- References
- 1. Kircun ME. Imaging of bone tumors. Philadelphia: W.B. Saunders, 1993: 311-312.
2. Fibrous dysplasia, Radiographics 1990; 10: 519-537.
- Keywords
- Rib, Benign tumor,