Figure 2A. Benign enchondroma. Anterior (left) and lateral (right) radiographs of the left femur showing an area of mottled calcification in the distal femoral shaft with slight expansion of the cortex. Differential diagnosis includes benign enchondroma, central chondrosarcoma and infarct.
Figure 2B. Benign enchondroma. Radiophosphate bone image shows a nonspecific intense focus of uptake. A benign enchondroma was removed at surgery.

as a small lucent defect which is eccentrically located in the metaphyseal cortex of a long bone. It usually heals spontaneously and the bone scan is invariably normal, unless complicated by a fracture. Nonossifying fibromas are larger in size and may be located in the metaphysis or diaphysis of a long bone. Bone scans are usually normal, but low grade uptake has been reported.

Fibrous Dysplasia

Fibrous dysplasia is a benign tumor in which masses of fibroblasts and islands of sarcomatous transformation. The lesions tend to stabilize at puberty. Of the solitary lesions, three-quarters are located in the ribs, femora, tibiae, skull and facial bones. The radionuclide manifestation is that of intense radiophosphate uptake in the lesion, indistinguishable from malignant tumors. About 10% to 15% of the lesions seen by radiography are reported to be negative by bone scan.

Giant Cell Tumor

Giant cell tumor appears to arise from non-bone forming supporting tissue, and histologically demonstrates a distinctive neoplasm composed of a vascularized network of spindle or ovoid stromal cells interspersed with multinucleated giant cells. Most frequently they occur in the third to fourth decades of life, but it has been described in the immature skeleton. It usually presents as an osteolytic process in the epiphyseal end of a long bone, particularly the distal femur and proximal tibia, in a skeletally mature patient. It comprises less than 5% of all primary tumors, and 90% of them are benign. Most giant cell tumors depict an avid uptake of radiophosphate. There is a 50%-60% recurrence rate following surgery, and about a 15% chance of converting to a malignant state. Many are hypervascular and are seen as such in the first segment of the three-phase bone scan (Fig. 3). This hyperemia may extend to the uninvolved bone adjacent to the joint, the so-called "extended" uptake.


Hemangioma of bone is a benign, slowly growing tumor emanating from newly formed blood vessels. There are cavernous and capillary types. Cavernous hemangiomas are commonly located in the vertebrae and skull, whereas the capillary variety is more likely to be encountered in flat bones and the metaphyses of long bones. In the spine, the radiographic appearance of cavernous hemangiomas is that of exaggerated vertical trabeculae or collapse of the vertebral body. Radiophosphate scans are variable. The three-phase bone study may show increased perfusion coupled with photopenia on delayed views.


Osteoblastoma is an uncommon, solitary lesion that is characterized by vascular osteoid and bone forming matrix rich in osteoblasts. It is closely related to osteoid osteoma, but differs in that it is larger (exceeding 2 cm) and reactive sclerosis is slight. Osteoblastomas constitute about 1% of all primary bone tumors and 3% of benign bone tumors, and affect patients between 10 and 30 years of age. About 50% are found in the vertebral column and skull, followed by the long bones, although they may be found at any site. The tumors do not regress spontaneously and may exhibit progressive growth. There are few reports of malignant transformation. Benign osteoblastomas avidly concentrate radiophosphate and are positive in both the blood pool and delayed phases.


Osteochondroma is a common tumor accounting for approximately half of all benign bone neoplasms and can be solitary or multiple. They arise in areas near the epiphyseal growth plates especially in the distal femur and proximal tibia. Radiographically, they appear as external nodular protuberances from or partially embedded in bone, and are characterized by an osseous stalk capped by hyaline

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