Chondrosarcoma of the Scapula.

A 63 year old female presents with a large , partly ossified soft tissue mass around the left scapula at the site of a presumed small osteochondroma.

A 63 year old female presented with an 8 month history of diffuse swelling around the left shoulder.On examination there was prominence of the wing of the left scapula with a suggestion of an underlying sub-scapular mass.Radiographs of the left scapula (Fig 1a) showed a large,partially ossified , sub-scapular soft tissue mass.Review of a chest radiograph performed 10 years previously following a myocardial infarction (Fig 1b) demonstrated a small osteochondroma arising from the inferior angle of the left scapula.CT of the scapula (Fig 2) confirmed a large,well-defined -tissue mass containing multiple foci of ossification and calcification.The tumour which arose from a broad-based osseous lesion on the undersurface of the scapula was compatible with a chondrosarcoma.Technetium 99 methyldiphosphonate (MDP) (Fig 3) showed increased uptake in the left scapula only and CT examination of the thorax showed no pulmonary metastases.Magnetic resonance (MR) imaging of the left scapula (Fig 4) confirmed a large well-defined,lobulated soft-tissue mass in the sub-scapular region which abutted the chest wall but did not extend into the glenohumeral joint or axillary vessels.It exhibited intermediate signal intensity on T1-weighted images.T2-weighted images clearly showed the lobulated structure and demonstrated predominantly increased signal intensity of the tumour with areas of low signal corresponding to areas of ossification / calcification on CT.Following intravenous gadolinium DTPA there was septal-nodular tumour enhancement with large central areas showing no enhancement suggesting the presence of cartilage,necrosis or myxoid change.Percutaneous biopsy under CT guidance (not shown) showed a grade 2 chondrosarcoma with large areas of myxoid change.The patient underwent an uneventful scapulectomy.

Chondrosarcomas most commonly affect the long tubular bones and the pelvis , the scapula being involved in approxiamately 5 % of cases (1).They can be classified in several ways.Primary chondrosarcomas occur in children and are uncommon.Secondary chondrosarcomas probably arise from a pre-existing benign cartilaginous lesion (either an osteochondroma or enchondroma) and occur in adults (2).Classic chondrosarcomas can be subdivided into central or peripheral types ( depending whether they arise from the medullary cavity or from the surface of the bone)and subsequently into 3 histological grades.There are also rare types such as clear cell,mesenchymal and dedifferentiated chondrosarcoma.Most peripheral chondrosarcomas probably originate from osteochondromas , particularly the sessile type ,however,only a minoritory of osteochondromas are thought to undergo malignant change . Although the presence of a large soft-tissue mass which engulfs and partly destroys the underlying osteochondroma ,as in the above case , is highly suggestive of malignant transformation , distinguishing a benign cartilaginous tumour from one which has undergone malignant transformation can be difficult (2).Location in the axial skeleton and size greater than 5 cm are the most reliable predictors of malignant change (3).Morphological features seen on radiographs and clinical symptoms are not reliable in distinguishing between benign and malignant cartilaginous tumours. Even histologically it can be difficult to distinguish low grade chondrosarcomas from benign osteochondromas and enchondromas.Chondrosarcomas which arise from malignant transformation of osteochondromas are predominantly large extraosseous masses which appear well defined even though they have invaded the soft tissues (1).MR is the imaging method of choice,the lobules of cartilage in the tumour showing a typical high signal on T2W images (2)and rapid enhancement on gadolinium-enhanced MR imaging is used to distinguish chondrosarcomas from benign cartilaginous tumours. (4).The appearances on scintigraphy are non-specific and its primary role is in excluding multifocal disease.