Rib malignancies masquerading as benign mediastinal tumours

Abstract

Mediastinal tumours are commonly encountered in general thoracic surgery practice. Benign tumours like thymoma and teratoma often need direct surgical resection if resectable. Pre-operative biopsy is not recommended. We report 2 cases which were radiologically diagnosed as thymoma and teratoma turned out to be Ewing sarcoma and chondrosarcoma respectively after surgical excision. This has challenged the notion whether biopsy is really not needed. More elaborate studies are needed to find out tumour characteristics which would warrant a biopsy even if they are resectable. In our cases, pre-operative biopsy would have changed the line of management in both patients. This has led to a change in institutional protocol that now, we do biopsy for any mediastinal tumour more than 8 cm and abutting the chest wall.

Keywords: Chondrosarcoma; Ewing sarcoma; Mediastinum; Teratoma; Thymoma.

Fig. 1

a Chest radiograph showing a large mass in the left hemi-thorax (blue star). b Computed tomogram (CT) showing a large anterior mediastinal mass with possible infiltration of the pulmonary artery (white arrow). c CT showing no signs of the tumour arising from the rib (yellow arrow). d Magnetic resonance imaging (MRI) showing preserved fat planes between the tumour and the pulmonary artery (white arrow)

Fig. 2

a Photomicrograph displaying sheets of round tumour cells, haematoxylin eosin (HE), 40 × . b Photomicrograph displaying sheets of round tumour cells, HE, 400 × . c Photomicrograph displaying sheets of round tumour cells showing membrane brown staining with CD99 immunohistochemistry (IHC), 400 × . d Photomicrograph displaying sheets of round tumour cells showing nuclear brown staining with NKX2.2 IHC, 400 ×

Fig. 3

a Computed tomogram (CT) showing a large tumour arising from the mediastinum with fat and calcific densities suggestive of teratoma (yellow star). The trachea is significantly compressed. b Photomicrograph displaying cartilaginous tumour arranged in varying sized lobules (400 ×). c Photomicrograph displaying tumour lobules entrapping the bony trabeculae (400 ×). d CT showing the tumour in close contact with the second rib but with no evidence suggesting that it is the origin (yellow arrow)