a 49-year - old man in whom a mediastinal mass had been present for twenty years was admitted to hospital , complaining chiefly of hemoptysis .
surgery had been recommended , but he had refused this option , denying up to the time of hospitalization any symptoms related to this lesion .
chest radiograph revealed a 1012 cm mass in the anterior mediastinum , as well as ill - defined consolidation in the left upper lobe .
contrast - enhanced ct scanning demonstrated a lobulated , inhomogeneous cystic mass with a fat component ( hu = -45 ) and calcified wall in the anterior mediastinum .
the lateral wall of the mass was focally disrupted and consolidation with the fat component in the adjacent left upper lobe was noted , thus suggesting that the tumor had ruptured ( fig .
an inhomogeneously enhanced solid portion was noted in the medial aspect of the mass and extended to the upper mediastinum , obliterating the fat plane between the mass and the mediastinal vessels ( fig .
thoracotomy demonstrated that the mass was rubbery , with hard components , and invaded the right brachiocephalic artery , the innominate vein , the ascending aorta , and the pericardium .
the mass had ruptured into the left upper lobe , but due to extensive invasion by vessels , was incompletely resected
. decompression and plication of the left upper lobe was performed , and pathologic examination showed that the excised mass was a 108 cm cystic tumor with a rugged , pale brown external surface .
it contained yellowish brown material with a few hair like structures , and cut section revealed a round , pale gray solid area in the wall that was firmly attached to the mediastinal structures .
microscopically , while most of the mass was mature teratoma with hemorrhage and necrosis ( fig .
1c ) , the solid portion of the wall was found to be poorly differentiated adenocarcinoma ( fig .
one month after surgery , the tumor recurred at the resected site , despite chemotherapy and subsequently metastasized .
although teratoma is commonly found both in gonadal organs and at extragonadal sites such as the mediastinum , sacrococcygeum and pineal region , tmt is rarely found in any organ . according to the literature , malignant transformation occurs in 1 - 2% of ovarian dermoid cysts examined ( 5 , 6 ) , though little is known about the general incidence and pathologic features of tmt in the mediastinum .
most malignant transformations of mediastinal teratomas have occurred , subsequent to chemotherapy or irradiation in young patients initially presenting with a malignant germ - cell tumor ( 1 , 2 ) .
( 3 ) described a surgical case of mediastinal teratoma with poorly differentiated adenocarcinoma , and two surgical cases of tmt were observed in a study by knapp et al .
characteristically , naturally occurring tmt is seen more frequently in older patients , with a peak incidence in the fifth and sixth decades of life .
secondary , probably multiple , genetic events may have elicited malignant transformation of a benign teratoma among patients in whom this had been present for a long period ( 3 ) .
tmt is usually very aggressive and as a result of local spread , metastasis , or both , is fatal within a few months of initial diagnosis ( 3 , 8) .
ct demonstrates that mediastinal mature teratoma typically manifests as a heterogeneous , sharply marginated , spherical or lobulated anterior mediastinal mass with cystic components ( 8) . to our knowledge
, the imaging features of mediastinal tmt have never been discussed in the literature . in morinaga 's report ( 3 ) , the solid papillary portions have also seen within a cystic mass were malignant foci .
chadha et al ( 5 ) and curling et al ( 6 ) have also reported that malignant ovarian tmt was found in a solid area in the wall of a mature teratoma . in our case , the malignant focus
was also found in the solid portion of the wall of the cystic mature teratoma .
the medial wall of the tumor abutting the great vessel was indistinct and thick in our case , whereas in 91% of cases , a benign mature teratoma has been shown to have a sharp margin and thin wall ( 8) .
if an invading solid portion with an indistinct margin is present in the wall of a mature teratoma , the possibility of tmt should therefore be considered .
the incidence of rupture of a benign teratoma is as high as 36% ( 4 ) , and several explanations as to why this tends to occur have been suggested .
we speculate that since pathologic examination revealed both hemorrhage and necrosis in the mass , the most probable cause of rupture of a tmt is ischemia
. rapid growth of the malignant portion of a tmt can result in ischemia , necrosis , and rupture of the teratoma ; the ct features of this latter are inhomogeneity of the internal components and changes in adjacent lung parenchyma , pleura , or pericardium , as in our case ( 9 ) . in summary
, we report a case of teratoma with malignant transformation in the anterior mediastinum , complicated by rupture .
a lobulated , inhomogeneous cystic mass was present , with a fat component and wall calcifications .
the wall of the mass had been disrupted , and consolidation with the fat component in adjacent lung was observed , indicating rupture . a heterogeneously enhanced solid portion was noted in the medial aspect of the mass ; this obliterated the fat plane between the mass and the great vessels , and was proven by pathologic examination to be adenocarcinoma .
 malignant transformation of teratoma in the anterior mediastinum is rare ; the mass usually has a long history and is seen in older patients . 
 we report a case of teratoma with malignant transformation in the anterior mediastinum , complicated by rupture . 
 ct revealed a lobulated , inhomogeneous cystic mass with a fat component and wall calcifications . the lateral wall was disrupted and consolidation in the adjacent left upper lobe was noted , suggesting rupture . a heterogeneously enhanced solid portion , obliterating the fat plane between the mass and the great vessels was present in the medial aspect of the mass , and pathologic examination demonstrated the presence of adenocarcinoma . 
CASE REPORT
DISCUSSION