[Pulmonary tumor thrombotic microangiopathy associated with cancer of unknown origin]

A nonsmoking, 52-year-old woman presented with a 4-month history of persistent dry cough. Chest X-ray film on admission showed small granular shadow in bilateral lung fields. Bronchoscopic biopsy did not yield a diagnosis. Two months later, she complained of dyspnea. Physical examination showed signs of pulmonary hypertension. Five days after the onset of dyspnea, she died of respiratory failure. An autopsy showed pulmonary embolism and swollen abdominal lymph nodes consisting of metastatic signet-ring cell carcinoma and poorly differentiated adenocarcinoma. There was also marked fibrocellular intimal proliferation and thrombus formation causing luminal stenosis in small pulmonary arterioles. Thrombi were organized by recanalization and included atypical cells. We diagnosed pulmonary tumor thrombotic microangiopathy (PTTM). In spite of various immunohistological staining procedure, we could not find out the primary lesion of this cancer. This case suggests that we should aggressively biopsy a large specimen of the lung to make a differential diagnosis of PTTM, because bronchoscopic biopsy is not enough to diagnose PTTM.