Juxta-cortical chondrosarcomas, also known as periosteal chondrosarcomas, are indistinguishable histologically from conventional medullary chondrosarcomas and are therefore graded into low, intermediate or high-grade tumors (see chondrosarcoma grading).
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Epidemiology
Typically it occurs in adults in their 3rd and 4th decades and is slightly more frequent in males.
Pathology
Unlike conventional chondrosarcomas, they arise from the surface of the bone, lifting the periosteum over themselves as a fibrous pseudocapsule. The underlying cortex is usually thickened or may be eroded, however, extension into the medullary cavity is not usual. Where the periosteum is lifted a Codman triangle may be seen. In addition to the usual chondroid matrix, metaplastic ossification is also common.
Location
They typically arise from long bones, with a predilection for the posterior aspect of the distal femur.
Differential diagnosis
-
periosteal osteosarcoma
- affects younger patients (typically 10-25 years of age)
- periosteal reaction perpendicular to the cortex
- diaphyseal rather than metaphyseal
-
parosteal osteosarcoma
- stalk of bony attachment
- otherwise similar appearance, location and demographics
- juxtacortical chondroma
- parosteal lipoma
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