teratomas are one of the common anterior mediastinal tumors and on imaging demonstrate soft tissue , fluid , fat , calcification or a combination of these . complications developing from these tumors are rare and imaging plays a vital role in the detection of these complications . we present two cases of spontaneous pulmonary and pleural rupture of benign mediastinal teratoma and discuss the imaging hints for its preoperative detection . a 19-year - old male presented with history of cough with scanty expectoration for 4 months and history of chest pain on right side for 3 days . there was dull note on percussion and reduced breath sounds on the right side of chest . chest radiograph ( not shown ) showed opaque right hemithorax with shift of the mediastinum to the left . contrast enhanced computed tomography ( ct ) scan [ figure 1 ] showed a heterogeneous mass in the anterior mediastinum with small focus of fatty attenuation ( hu of -36 ) within . there was gross right - sided pleural effusion , with near complete collapse / consolidation of the right lung and the pleural fluid showed fatty attenuation in its anterior aspect [ figure 1 ] . magnetic resonance imaging ( mri ) of the chest done for further characterization of the mediastinal lesion showed heterogeneous mass with hypointense capsule on t2-weighted images [ figure 2 ] . on t1-weighted images , there was an area of hyperintensity that showed signal suppression on fat - saturated images [ figure 3 ] . based on the imaging features , a diagnosis of mediastinal teratoma with spontaneous pleural and pulmonary rupture was made . the mass was encapsulated and showed an area of rupture into the lung ; the pleural fluid was thick and yellow and showed internal septations . the middle - right lobe bronchus was separate from the mass with no evidence of bronchial communication . axial contrast enhanced ct scan shows a heterogeneous mass in the anterior mediastinum containing an area of fat ( black arrow ) and air pockets ( arrow heads ) . the mass is closely abutting the middle - right lobe bronchus ( white arrow ) . gross pleural effusion with underlying lung collapse / consolidation is noted on the right side . a caudal section ( b ) shows freely floating fat tissue in the pleural fluid ( arrows ) axial t2-weighted image showing the mediastinal mass ( arrows ) with thick hypointense capsule and heterogeneous internal architecture . right pleural effusion ( * ) is noted coronal t1-weighted gradient echo images without ( a ) and with ( b ) fat saturation . pleural effusion is also seen ( * ) a 15-year - old male presented with history of gradual onset dyspnoea on exertion for 6 months . patient was diagnosed to have an anterior mediastinal mass 3 years ago , but had refused surgery . physical examination revealed volume loss of right hemithorax with decreased breath sounds and coarse crepitations . chest radiograph revealed airspace opacity with air - bronchogram in right hemithorax [ figure 4a ] . chest radiograph which was taken 3 years earlier showed a well - defined mediastinal - based mass on the right side , silhouetting the ascending aorta , suggesting its anterior location [ figure 4b ] . contrast enhanced ct scan revealed a heterogeneous anterior mediastinal mass with areas of soft tissue and fat density . the mass was extending into the adjacent right lung causing its consolidation with areas of fat density within consolidation . mri was done prior to surgery that showed a fat intensity ( hyperintense on t1 weighted images with suppression of signal on fat suppressed t1 weighted images ) lesion in the anterior mediastinum involving the right lung with adjacent areas of consolidation [ figures 5a and b ] . chest radiograph ( a ) shows consolidation with airbronchogram in the right lung . chest radiograph ( b ) obtained 3 years ago demonstrates a well - defined anterior mediastinal mass on the right side ( arrows ) . the right lung is normal axial t1 weighted ( a ) and t1 weighted - fat suppressed ( b ) images show a heterogeneous fat intensity ( hyperintense on t1w and show suppression on fat suppressed t1w images ) lesion in the anterior mediastinum ( arrow ) with extension into the right lung showing areas of consolidation ( asterix ) a 19-year - old male presented with history of cough with scanty expectoration for 4 months and history of chest pain on right side for 3 days . there was dull note on percussion and reduced breath sounds on the right side of chest . chest radiograph ( not shown ) showed opaque right hemithorax with shift of the mediastinum to the left . contrast enhanced computed tomography ( ct ) scan [ figure 1 ] showed a heterogeneous mass in the anterior mediastinum with small focus of fatty attenuation ( hu of -36 ) within . there was gross right - sided pleural effusion , with near complete collapse / consolidation of the right lung and the pleural fluid showed fatty attenuation in its anterior aspect [ figure 1 ] . magnetic resonance imaging ( mri ) of the chest done for further characterization of the mediastinal lesion showed heterogeneous mass with hypointense capsule on t2-weighted images [ figure 2 ] . on t1-weighted images , there was an area of hyperintensity that showed signal suppression on fat - saturated images [ figure 3 ] . based on the imaging features , a diagnosis of mediastinal teratoma with spontaneous pleural and pulmonary rupture was made . the mass was encapsulated and showed an area of rupture into the lung ; the pleural fluid was thick and yellow and showed internal septations . the middle - right lobe bronchus was separate from the mass with no evidence of bronchial communication . axial contrast enhanced ct scan shows a heterogeneous mass in the anterior mediastinum containing an area of fat ( black arrow ) and air pockets ( arrow heads ) . the mass is closely abutting the middle - right lobe bronchus ( white arrow ) . gross pleural effusion with underlying lung collapse / consolidation is noted on the right side . a caudal section ( b ) shows freely floating fat tissue in the pleural fluid ( arrows ) axial t2-weighted image showing the mediastinal mass ( arrows ) with thick hypointense capsule and heterogeneous internal architecture . right pleural effusion ( * ) is noted coronal t1-weighted gradient echo images without ( a ) and with ( b ) fat saturation . a 15-year - old male presented with history of gradual onset dyspnoea on exertion for 6 months . patient was diagnosed to have an anterior mediastinal mass 3 years ago , but had refused surgery . physical examination revealed volume loss of right hemithorax with decreased breath sounds and coarse crepitations . chest radiograph revealed airspace opacity with air - bronchogram in right hemithorax [ figure 4a ] . chest radiograph which was taken 3 years earlier showed a well - defined mediastinal - based mass on the right side , silhouetting the ascending aorta , suggesting its anterior location [ figure 4b ] . contrast enhanced ct scan revealed a heterogeneous anterior mediastinal mass with areas of soft tissue and fat density . the mass was extending into the adjacent right lung causing its consolidation with areas of fat density within consolidation . mri was done prior to surgery that showed a fat intensity ( hyperintense on t1 weighted images with suppression of signal on fat suppressed t1 weighted images ) lesion in the anterior mediastinum involving the right lung with adjacent areas of consolidation [ figures 5a and b ] . chest radiograph ( a ) shows consolidation with airbronchogram in the right lung . chest radiograph ( b ) obtained 3 years ago demonstrates a well - defined anterior mediastinal mass on the right side ( arrows ) . the right lung is normal axial t1 weighted ( a ) and t1 weighted - fat suppressed ( b ) images show a heterogeneous fat intensity ( hyperintense on t1w and show suppression on fat suppressed t1w images ) lesion in the anterior mediastinum ( arrow ) with extension into the right lung showing areas of consolidation ( asterix ) rupture of mediastinal teratoma is a rare complication , occurring in up to 36% of cases , most frequently into lung and the tracheobronchial tree , followed by pleura , pericardium , and great vessels.[25 ] patients may present with hemoptysis , chest pain , or expectorate hair or sebaceous material . among the various hypotheses proposed to explain the possible mechanisms of rupture , the most commonly accepted theory is autolysis of the walls of the tumor by the digestive enzymes produced by tissues ( pancreas , intestine , salivary gland ) leading to rupture . however , after rupture , it becomes inhomogeneous probably due to the development of secondary inflammatory reaction . such a change in the appearance of the mass can also be depicted on mri , as was seen in one of our cases . other imaging findings of rupture include consolidation or atelectasis of adjacent lung and pleural or pericardial effusion . a fat - fluid level in the pleural effusion after rupture has also been reported . ruptured teratomas may mimic the imaging findings of malignant teratomas like spiculated borders , thick capsule , heterogeneous contents , and obliteration of fat plane . ruptured components of the teratoma cause inflammation and secondary adhesions in the lung or pleural cavity . this makes surgery challenging and a preoperative diagnosis helps in judicious planning of the time and approach of surgery . in our cases , heterogeneous appearance of the mass , changes in the surrounding lung , or effusion suggest rupture in an acute clinical scenario .
benign mediastinal teratomas are commonly asymptomatic and seldom cause complications . 
 spontaneous rupture into the pleura is rare and cross - sectional imaging is crucial in its early detection and planning a proper surgical approach . 
 we report two cases of spontaneous pulmonary and pleural rupture of benign mediastinal teratoma and discuss the imaging appearances .