Chondrosarcoma

Chondrosarcomas are malignant cartilaginous tumours that account for ~25% of all primary malignant bone tumours. They are most commonly found in older patients within the long bones, and can arise de novo or secondary from an existing benign cartilaginous neoplasm. On imaging these tumours have ring-and-arc chondroid matrix mineralisation with aggressive features such as lytic pattern, deep endosteal scalloping and soft-tissue extension. 

Epidemiology

Typical presentation is in the 4th and 5th decades and there is a slight male predominance of 1.5-2:1.

Clinical presentation

Patients usually present with pain, pathological fracture, a palpable lump or local mass effect. Hyperglycaemia can occur as a paraneoplastic syndrome.

Pathology

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 endochondral ossification. This accounts not only for the high T2 MRI signal (see below) but also for rings and arcs calcification or popcorn calcification.  

Grading

Chondrosarcomas are divided into three (sometimes four) grades based primarily on cellularity (see: chondrosarcoma grading).

Subtypes

Chondrosarcomas are either primary, arising de novo, or secondary and arise from a pre-existent cartilaginous mass (see: secondary chondrosarcoma).

Primary
Secondary

Arising from pre-existing cartilagenous lesions:

Distribution
  • 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
    • location
      • 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

Radiographic features

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 >4 cm in diameter and >10 cm in 50% of cases.

Plain radiograph
CT

The features seen on CT are the same as on plain film, but are simply better seen:

  • 94% of cases demonstrate matrix calcification, c.f. 60-78% on plain film
  • endosteal scalloping
  • cortical breach, seen in ~90% of long bone chondrosarcoma, c.f. only ~10% of enchondromas
  • soft tissue mass: density increases with increased grade of tumour do to increased cellularity
  • heterogenous contrast enhancment
MRI
  • 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
Nuclear medicine

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 latter has increased uptake in ~20% 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
    • grade 1: 90% 5-year survival
    • grade 3: 29% 5-year survival
  • location
    • long bones have a better prognosis than axial skeleton

Bone tumours

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.

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