Chondrosarcomas are malignant cartilaginous tumours that account for 20-27% of all primary malignant bone tumours. They are commonly found in long bones due a more abundant cartilage presence, and are diagnosed in patients in their 4th and 5th decades of life. There are two main subtypes: primary chondrosarcomas (de novo lesions) and secondary chondrosarcomas (superimposed on preexisting benign cartilaginous neoplasms).
On imaging these tumours have suggestive radiographic features such as lytic pattern, typical ring-and-arc chondroid matrix mineralization, deep endosteal scalloping and soft-tissue extension. CT additionally depicts the matrix mineralization. The high water content of these lesions are expressed as low attenuation on CT and very high signal intensity with T2-weighted MRI sequences. Contrast enhancement is heterogeneous and when more prominent and diffuse it frequently suggests more aggressive types of chondrosarcomas.
Typical presentation is in the 4th and 5th decades and there is a slight male predominance of 1.5-2:1.
The histology of chondrosarcomas can differ according to their sub type (see below). In general these tumours are multilobulated (due to hyaline cartilage nodules) with central high water content and peripheral enchondral ossification. This accounts not only for the high T2 MRI signal (see below) but also for rings and arcs calcification or popcorn calcification.
Chondrosarcomas are divided into 3 (sometimes 4) grades based primarily on cellularity (see chondrosarcoma grading).
Chondrosarcomas are either primary, arising de novo, or secondary and arise from a pre-existent cartilagenous mass: see secondary chondrosarcoma.
- conventional intramedullary chondrosarcoma (or central chondrosarcoma): low, intermediate or high grade (see chondrosarcoma grading)
- juxtacortical chondrosarcoma: low, intermediate or high grade
- clear cell chondrosarcoma
- myxoid chondrosarcoma: usually intermediate grade
- mesenchymal chondrosarcoma: usually high grade
- extraskeletal chondrosarcoma
- dedifferentiated chondrosarcoma
Arising from pre-existing cartilagenous lesions:
- solitary osteochondroma
- hereditary multiple exostoses (also known as diaphyseal aclasis)
- long bones: 45% (the reason is because the cartilage is more abundant in the long, tubular bones).
- pelvis: 25% especially around the triradiate cartilage
- ribs: 8%
- patients often younger than at other sites
- anterior ribs/costochondral junction
- spine: 7%
- greater male predominance 2-4:1
- thoracic most common
- posterior elements and vertebral body 45%
- posterior elements only 40%
- vertebral body only 15%
- scapula: 5%
- sternum: 2%
- head and neck (including cervical spine): 6-7%
- craniofacial: 2% (see chondrdosarcoma of the skull of base)
- hands and feet: rare c.f. enchondromas
Imaging findings vary somewhat with different sub types but do have some general features. Below are typical imaging appearances which are best demonstrated by conventional chondrosarcomas.
In general chondrosarcomas are large masses at the time of diagnosis, usually over 4 cm in diameter and over 10 cm in 50% of cases.
- lytic (50%)
- intralesional calcification(s): 60-78% (rings and arcs calcification or popcorn calcification)
- endosteal scalloping: affecting more than two thirds of the cortical thickness (c.f. less than 2/3 in enchondromas)
- moth eaten appearance or permeative appearance in higher grade tumours (see chondrosarcoma grading), e.g myxoid, dedifferentiated and mesenchymal chondrosarcomas
- cortical remodelling, thickening and periosteal reaction are also useful in distinguishing between an enchondroma and low grade chondrosarcoma (see enchondroma vs. low grade chondrosarcoma)
The features seen on CT are the same as on plain film, but are simply better seen.
- 94% of cases demonstrate matrix calcificaiton, c.f. 60-78% on plain film.
- endosteal scalloping
- cortical breach, seen in 88% of longbone chondrosarcoma, c.f. only 8% of enchondromas
- soft tissue mass: density increases with increased grade of tumour do to increased cellularity
- heterogenous contrast enhancment
T1: low to intermediate signal
- iso- to slightly hyperintense cf. muscle
- iso- to slightly hypointense cf. grey matter (see chondrosarcoma of the base of skull)
- T2: very high intensity in nonmineralised/calcified portions
- gradient echo/SWI: blooming of mineralised/calcified portions
T1 C+ (Gd)
- most demonstrate heterogeneous moderate to intense contrast enhancement.
- enhancement can be septal and peripheral rim-like corresponding to fibrovascular septation between lobules of hyaline cartilage
Typically chondrosarcomas demonstrate increased uptake on bone scan, seen in over 80% of cases, and usually the uptake is quite intense. This is useful in helping to distinguish a low grade chondrosarcoma from an enchondroma as the later has increased uptake in only 21% of cases, and usually to a lesser degree. (see enchondroma vs. low grade chondrosarcoma)
Treatment and prognosis
Prognosis varies with both grade and location. In general:
- grade 1: 90% 5 year survival
- grade 3: 29% 5 year survival
- long bones have a better prognosis than axial skeleton
The differential diagnosis for bone tumours is dependent on the age of the patient, with a very different set of differentials for the paediatric patient.
- bone-forming tumours
- enchondromatosis (Ollier disease)
- Maffucci syndrome
- chondromyxoid fibroma
- fibrous bone lesions
- bone marrow tumours
- other bone tumours or tumour-like lesions
- simple bone cyst
- aneurysmal bone cyst
- benign fibrous histiocytoma
- haemophilic pseudotumour
- giant cell tumour of bone
- primary intraosseous haemangioma
- intraosseous lipoma
- musculoskeletal angiosarcoma
- Gorham massive osteolysis
- impending fracture risk
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- 2. Meyers SP, Hirsch WL, Curtin HD et-al. Chondrosarcomas of the skull base: MR imaging features. Radiology. 1992;184 (1): 103-8. Radiology (abstract) - Pubmed citation
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- 4. Murphey MD, Walker EA, Wilson AJ et-al. From the archives of the AFIP: imaging of primary chondrosarcoma: radiologic-pathologic correlation. Radiographics. 23 (5): 1245-78. doi:10.1148/rg.235035134 - Pubmed citation
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