. Findings 128. OrthopaedicsOne Images. In: OrthopaedicsOne - The Orthopaedic Knowledge Network. Created Feb 12, 2010 19:37. Last modified Jun 27, 2011 11:34 ver.7. Retrieved 2019-04-24, from https://www.orthopaedicsone.com/x/zYWmAQ.
Here is an entirely lytic lesion arising eccentrically in the distal tibia. The lesion has its epicenter in the metaphysis but has expanded through the epiphyseal region to involve the subarticular cortex. The lesion is interesting in that it is geographic with a narrow zone of transition but does not have a sclerotic margin. CT was performed (though not required for diagnosis or treatment in this case). The CT (Films .3 and .4) demonstrates that the lesion had been slightly expansile with thinning of the overlying cortex. The overlying cortex was thinned to the point where in some portions of the CT the rim is no longer seen. However, extrapolating from the remaining rim, there is no soft tissue mass extending beyond the expanded portion of the lesion. This confirms the expansile but only mildly aggressive nature of this lesion. CT confirms the absence of matrix calcification.
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This case represents a classic giant-cell tumor. A giant-cell tumor consists of multinucleated giant cells within a fibroid stroma. They are distinct from many other lesions which histologically may contain reactive giant cells. The lesion is usually radiographically distinct and easily recognized. As seen in this case, it is a geographic expanding lesion which is located eccentrically in the metaepiphyseal region. While the site of origin is the metaphysis, it later extends to the subarticular end of the bone, and it is this feature that we note as distinct in giant-cell tumor. Another distinctive feature is the fact that while the lesion is geographic with a narrow zone of transition, it almost never has a sclerotic margin. This combination of narrow zone of transition and lack of a sclerotic margin is a highly reliable feature of giant-cell tumor that is rarely seen in other lesions.
The lesion nearly always occurs after epiphyseal fusion and most often occurs between the ages 20 and 40. However, the diagnosis should not be excluded in either the younger or older population. The most common sites of involvement are about the knee (distal femur and proximal tibia) or wrist (distal radius or ulna). It occasionally involves metaphyseal equivalent sites in flat bones and may involve the spine, usually the sacrum or vertebral bodies. In the absence of fracture, there is rarely host response.
Although giant-cell tumors are usually easily diagnosed, they can be confused with other lesions. In a patient who is just becoming skeletally mature, a lesion located in the epiphysis and metaphysis could represent either a chondroblastoma or giant-cell tumor. Generally, chondroblastomas have more of a sclerotic margin. Another item in the differential diagnosis of giant-cell tumor is a brown tumor of hyperparathyroidism. These lesions certainly can have similar appearances, but one would hope to find other signs of hyperparathyroidism such as subperiosteal resorption. Non-ossifying fibromas are metaphyseally located eccentric lesions. However, they usually have a sclerotic border and should be easily differentiated from giant-cell tumors. An intermedullary chondrosarcoma which has little or no calcified matrix and is located in the metaepiphyseal region could masquerade as a giant-cell tumor (see Case 125). Finally, in the slightly older age group, a plasmacytoma located in the metaphyseal region could be misinterpreted as a giant-cell tumor. Plasmacytomas often initially have no cortical breakthrough and no soft tissue mass. They may also have the characteristic of a narrow zone of transition but no sclerotic margin.