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).
Typically it occurs in adults in their 3and 4 decades and is slightly more frequent in males.
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.
They typically arise from long bones, with a predilection for the posterior aspect of the distal femur.
- 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