pulmonary tumor thrombotic microangiopathy ( pttm ) also known as carcinomatosis endarteritis is a highly fatal respiratory complication seen in cases of malignancies especially adenocarcinomas of the stomach .
there are only around 80 cases reported in literature so far including less than 10 cases where the primary malignancy has not been detected even after extensive search .
we present an autopsy case of a 47-year - old male patient who developed acute breathlessness and died suddenly . at autopsy
there was mild right ventricular dilatation and lungs showed few firm areas and prominent bronchovasculature .
on microscopy , the lungs showed the presence of florid fibrocellular intimal proliferation of the arterioles and small arteries [ figure 1 ] .
vessels showed fibrin thrombi and occasional vessel showed tumor emboli composed of neoplastic adenocarcinoma cells showing glandular and occasional signet ring morphology .
there were similar tumor emboli in the myocardium , peripancreatic tissue , and perigastric lymph nodes [ figure 3 ] . despite extensive sectioning no primary tumor
tumor cells were negative for ck 7 , ck10 , ttf 1 , and psa .
the final cause of death was given as acute cor pulmonale following pulmonary tumor thrombotic microangiopathy in an unknown primary adenocarcinoma .
lungs showing presence of florid fibrocellular intimal proliferation with fibrin thrombi of the arterioles and small arteries ( h and e , 100 ) lungs showing presence of lymphangiosis carcinomatosis ( h and e , 100 ) signet ring cells seen in the lymph nodes ( h and e , 400 )
pttm is characterized by intimal proliferation in pulmonary small arteries and arterioles with or without tumor emboli leading to vascular stenosis and pulmonary hypertension .
there was florid fibrointimal proliferation , fibrin thrombi with some showing occasional tumor emboli and lymphangimatosis carcinomatosis .
the tumor cells in this condition invade the pulmonary vascular system occluding the small arteries , arterioles and activate coagulation systems releasing inflammatory mediators , growth factors like serotonin , vascular endothelial growth factor and osteopontin .
some authors have proposed screening with serum vegf and d - dimer testing for early detection of pttm .
the primary sites of malignancy reported are gastrointestinal tract , ovary , breast , pancreas , liver , uterus , gall bladder , and prostate .
however , rarely there are reported cases where primary has not been detected inspite of extensive search and immunohistochemical stains . in our case too despite an extensive search no primary mass was found .
thus , our case belongs to the rare set of pttm with unknown primary of which only less than 10 cases have been reported .
it should be distinguished from ordinary pulmonary thromboembolism and primary pulmonary hypertension and should be considered as a differential diagnosis in patients with acute respiratory symptoms especially in cases with an underlying cancer .
there are only occasional case reports of antemortem diagnosis with patient recovering completely , and hence it is important to have a higher clinicopathological awareness of diagnosing this highly fatal condition .
role of 2-(f-18)-fluoro-2-deoxy - d - glucose positron emission tomography ( fdg - pet ) has been described in literature and has been described to be helpful for the diagnosis of pttm .
 pulmonary tumor thrombotic microangiopathy ( pttm ) is a highly fatal complication of cancer leading to acute cor pulmonale and pulmonary hypertension . 
 we present a case of 47-year - old male patient who developed acute breathlessness and died suddenly . 
 the pulmonary vessels at autopsy on histopathologic examination showed the presence of fibrocellular intimal proliferation , fibrin thrombi and few tumor emboli consisting of malignant adenocarcinoma cells . 
 there was associated lymphangiosis carcinomatosis . 
 no primary visceral tumor was found despite extensive search . 
 the patient had died following acute cor pulmonale with sudden pulmonary hypertension due to pttm . 
 this entity ( pttm ) must be kept as a differential diagnosis in patients presenting with acute breathlessness especially in cases of cancers . 
INTRODUCTION
CASE REPORT
DISCUSSION