malignant mesothelioma is a neoplasm that originates from the mesothelial cells lining the pleura , peritoneum , tunica vaginalis of the testis and pericardium ( 1 ) . primary pericardial mesothelioma is extremely rare , accounting for 0.8% of all cases of mesothelioma and 2 - 3% of all pericardial tumors ( 1,2 ) . the diagnosis of pericardial mesothelioma is difficult and it is usually only made at autopsy . patients mostly present with dyspnea on exertion caused by an accumulation of pericardial effusion ( 3 ) , and the prognosis is very poor with a median survival period of six months from diagnosis ( 4 ) . we herein report a patient with primary pericardial mesothelioma who showed a long survival without any aggressive treatment after the onset of cardiac tamponade . a 67-year - old japanese man with a smoking history of 50 pack years was taken by ambulance to a local hospital in january 2010 because of palpitation and dyspnea that had worsened over the course of a week . an echocardiographic examination revealed significant pericardial effusion with right ventricular diastolic collapse suggestive of cardiac tamponade . chest radiography revealed an enlargement of the cardiac silhouette and bilateral pleural effusion ( fig . electrocardiography demonstrated a sinus rhythm of 100 beats per minute and a low - voltage qrs complex . computed tomography ( ct ) demonstrated pericardial and bilateral pleural effusion without any tumorous lesions on the pleura or pericardium , or in the lung ( fig . emergency pericardiocentesis was performed under echocardiographic guidance to achieve an improvement of his circulatory dynamics , and bloody pericardial effusion was drained ( fig . although a cytological examination revealed a tiny amount of atypical cells suggestive of malignancy , the information obtained was inadequate to make a definitive diagnosis ( fig . one week after pericardiocentesis , ultrasonography and chest radiography demonstrated a reaccumulation of the pericardial effusion . surgical pericardial fenestration and pericardial biopsy were to create a window to the left thoracic cavity and thus make a histological diagnosis . macroscopically , the parietal pericardium had become diffusely thickened measuring approximately 8 mm in thickness , while the visceral pericardium showed a thickness of approximately 5 mm ( fig . furthermore , the pleural surface was smooth any without nodular lesions . a histological examination of the resected pericardium specimen revealed spindle - shaped atypical cells with nucleoli among infiltrating lymphocytes ( fig . 2c and d ) . immunohistochemistry showed the atypical cells to be diffusely positive for cam5.2 and wt1 , focally positive for calretinin , and negative for ttf-1 ( fig . although these findings suggested the possibility of malignant sarcomatoid mesothelioma , distinguishing the specimen from reactive mesothelial cells proved to be impossible . after pericardial fenestration , no reaccumulation of pericardial effusion occurred , and the patient was closely followed up thereafter . a : chest radiography demonstrated an enlarged heart shadow and bilateral pleural effusion . d : cytological findings of pericardial effusion showed a small amount of atypical cells suggestive of malignancy . a , b : macroscopically , there is thickening of the pericardium and no nodular lesion of the parietal or visceral pericardium or pleura . c , d : histologically , the resected pericardium specimen revealed spindle - shaped atypical cells with nucleoli among the infiltrating lymphocytes . chest radiography was performed in every two or three months for 21 months after discharge , there was no appearance of any tumorous lesion or effusion . however , multiple pleural tumors which were absent at least before three months emerged in the left thoracic cavity in november 2011 ( fig . 3a and b ) . ct - guided biopsy of the pleural tumor was performed , and a histological examination demonstrated malignant cells in the form of spindle - shaped cells showing similar features to the tissue obtained by pericardium biopsy at the onset of cardiac tamponade ( fig . moreover , these malignant cells were immunohistochemically identical to the samples collected previously from the pericardium , showing positivity for calretinin , wt1 , ae1/ae3 , and cam5.2 , and negativity for cea and ttf-1 . based on these findings , it was considered that these pleural tumors had likely resulted from the dissemination of pericardial mesothelioma cells due to pericardial fenestration of the left thoracic cavity . a , b : chest radiography and computed tomography demonstrated pleural tumors in the left thoracic cavity at 21 months after the onset of cardiac tamponade . c , d : histological findings demonstrated the presence of malignant spindle - shaped cells . the first - line systemic chemotherapy was a combination with cisplatin and pemetrexed every three weeks for four cycles , which resulted in a partial response , and then continued with maintenance pemetrexed monotherapy . however , after 14 cycles of pemetrexed maintenance therapy the tumor appeared in the cardiac chamber , and therefore second - line chemotherapy with carboplatin and gemcitabine was conducted every three weeks for three cycles . however , the disease progressed , and thereafter the patient received supportive care in the palliative care unit , and died in november 2013 . primary malignant pericardial mesothelioma is a highly unusual malignancy , with a reported prevalence of 0.0022% in an autopsy series ( 5 ) . pericardial mesothelioma can be categorized histologically as either epithelioid type , sarcomatoid type , biphasic type or desmoplastic type , as is the case for malignant pleural mesothelioma ( 6 ) . although pleural mesothelioma has been shown to be related to asbestos exposure , pericardial mesothelioma shows a less frequent association with asbestos ( 7 ) . several risk factors for pericardial mesothelioma have been reported , including infection with simian virus 40 , a genetic predisposition , and prior radiation therapy ( 8) . our patient had no history of asbestos exposure , and no asbestos bodies were evident in tissue samples of the pericardium and pleural nodule . furthermore , there was no evidence of any other risk factors , and therefore the pathogenesis of pericardial mesothelioma in this patient was unclear . cardiac decompensation is the most frequent initial symptom of pericardial mesothelioma , and this is caused by pericardial effusion , cardiac tamponade or constrictive pericarditis . pericardiocentesis or pericardial fenestration can be performed to alleviate the onset of heart failure , and a diagnosis can be made from specimens obtained in this way . however , it is difficult to morphologically distinguish malignant mesothelioma from reactive mesothelial cells , and the antemortem diagnostic yield is reported to be only 20% ( 9 ) . although our patient also exhibited cardiac decompensation due to pericardial effusion and therefore underwent palliative pericardiocentesis and pericardial fenestration , we were unable to make a definitive diagnosis of mesothelioma at the time that cardiac tamponade appeared . pleural dissemination was detected by a careful follow - up , thus allowing us to eventually make a diagnosis of malignant mesothelioma . the prognosis of pericardial mesothelioma is very poor and no standard treatment guidelines have been established . the median survival time from the first symptoms in the review was six months ( 10 ) . although resection may be curative in cases of localized disease , most cases are diagnosed at an advanced stage due to the lack of early symptoms . systemic chemotherapy is performed in cases of advanced malignant pericardial mesothelioma as well as pleural mesothelioma ( 11 ) . among the histological subtypes of mesothelioma , the sarcomatoid type shows a poor response to chemotherapy , and it is thus associated with metastasis and a short survival ( 12 ) . the present case was unusual in that the patient had a relatively long progression - free period without treatment , and received chemotherapy with cisplatin and pemetrexed only after the disease had progressed . the response was initially favorable , but this proved to only be a temporary phenomenon . in conclusion , we herein described a rare case of sarcomatoid type primary malignant pericardial mesothelioma with a long - term survival after the onset of cardiac tamponade . although pericardial mesothelioma is an uncommon malignancy , clinicians should include this possibility in the differential diagnosis when encountering patients with cryptogenic pericardial effusion .
primary pericardial malignant mesothelioma is a very rare clinical entity and its prognosis is very poor . 
 we herein report a 67-year - old man who presented with pericardial mesothelioma that was diagnosed 21 months after the onset of cardiac tamponade as the initial manifestation . despite undergoing pericardiocentesis and surgical pericardial fenestration at the onset of cardiac tamponade 
 , we were unable to make a conclusive diagnosis of mesothelioma based on the cytological and histological findings . 
 this unusual case had a relatively long progression - free period without treatment before the appearance of pleural tumors that showed the histological features of malignant sarcomatoid mesothelioma .