Intrathoracic low grade synovial sarcoma

Large intra-thoracic soft tissue mass lesion is seen centered upon the right apical paraspinal and paracardiac/para-mediastinal regions is seen measuring about 12 x 9.5 x 14 cm in maximum axial and CC diameters. Such mass lesion shows heterogenous post contrast enhancement with central hypodense non enhancing areas of breaking down. No internal calcifications. It has the following extensions and relations:

• medially: it is seen abutting the right lateral aspect of the trachea, indenting/compressing the SVC, IVC and abutting/attenuating the related right tracheo-bronchial tree along its inferior aspect  
• anterolaterally: it is seen resting upon the inner aspects of the related right upper ribs with no definite bony invasion
• posteriorly and superiorly: it is seen resting upon the inner aspect of the related upper ribs and seen inseparable from/engulfing small bony excrescence protruding from the anterior aspect of the 4^th rib near its costo-vertebral junction (arrow). Associated permeative osseous changes of the posterior 3^rd and 4^th ribs
• Inferiorly: it is seen indenting the right upper lung lobe and attenuating right upper lobe bronchus with underlying subsegmental atelectatic changes

Small left fissural based nodule is noted

Bilateral pulmonary patchy areas of parenchymal veiling intermingled with areas of air trapping

No CT evidence of hilar or mediastinal lymph node enlargement

Mildly enlarged liver

DIAGNOSIS:

A case of monophasic low grade synovial sarcoma

The tumor cells are positive for CD99 & BCL2  

They are negative for CD34, S100 protein