|Print Date:||May 22, 2013, 11:05 am|
|Text||Chondroblastic osteosarcoma, defined as a high-grade bone tumor with a substantial volume (greater than 90%) of tumor tissue with a chondrosarcomatous phenotype next to osteoid forming areas, is a rare tumor. The reported overall prevalence varies from 4.2% to 23.8% of all osteosarcomas. Differentiating chondroblastic osteosarcoma from conventional central osteosarcoma and from chondrosarcoma is of clinical importance because of substantial differences in treatment and prognosis. Chondrosarcomas are treated with curative intention by resection only. Osteosarcomas are treated with curative intention by resection combined with chemotherapy and have a poorer prognosis. In the case of a chondroblastic osteosarcoma, its extensive chondroid component not infrequently results in biopsy sampling errors and thus in an erroneous histologic pre-operative diagnosis of chondrosarcoma. Age however can help in the differential diagnosis. The median age of patients in a series reported by Geirnaerdt et al. was 23 years, which is closer to that of osteosarcoma (median 17 years) than that of chondrosarcoma (median 48 years).
Geirnaerdt et al. attempted to characterize chondroblastic osteosarcoma by gadolinium-enhanced MR imaging in a retrospective review of 9 histopathologically confirmed cases.
They concluded that there was no identifiable pattern of enhancement characteristic of chondroblastic osteosarcoma. The extensive septonodular enhancement pattern observed throughout well-differentiated chondrosarcomas was not a dominant feature in the cases of chondroblastic osteosarcomas they studied. They did see a heterogeneous enhancement pattern in both chondroblastic osteosarcomas and conventional osteosarcomas. They found that areas containing osteoid and chondroid matrix were both present in areas without enhancement, or with a heterogeneous pattern of enhancement. They further found that areas exhibiting septonodular enhancement or peripheral rim enhancement without heterogeneous enhancement centrally in the tumor, corresponded to tumor tissue with a chondroid phenotype only. Recognition of septonodular enhancement or peripheral enhancement is thus important for characterizing a lesion as one with substantial amounts of chondroid phenotype.
On the contrary, in tumor areas forming osteoid matrix only, no enhancement was seen despite marked cellularity and vascularity. Compared with the intense enhancement patterns of chondroid-forming tissue this suggests that Gd-DTPA prefers the chondroid matrix over the osteoid forming parts.
Hence to avoid a false diagnosis of chondrosarcoma, especially in a relatively young patient where chondroblastic osteosarcomas should be considered, biopsy sites should be selected by Gd-enhanced MR images and samples should be taken from central areas displaying either no enhancement or heterogeneous enhancement, because here both chondroid and osteoid can be found.
|References:||Geirnaerdt M. et al. Chondroblastic osteosarcoma: characterization by gadolinium enhanced MR imaging correlated with histopathology. Skeletal Radiology. 27(3):145-53, 1998 Mar.
Resnick. Diagnosis of Bone & Joint Disorders, 4th ed.
Mirra JM. Bone Tumors, 1989
Kissane JM. Andersonâ€™s Pathology, 9th ed.
|Contributor||Steve Kao (National Capital Consortium)|
|Peer Reviewer||Philip A Dinauer (Civilian Medical Center)|
|Record Number||: 6282|
|Category:||Neoplasm, malignant (NOS)|
|Location:||MSK - Musculoskeletal|
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