Pulmonary tumor thrombotic microangiopathy (PTTM) is an uncommon cancer-related complication characterized by intimal proliferation in pulmonary small arteries and arterioles with or without tumor emboli. In the majority of cases, the causative lesion is gastric poorly differentiated adenocarcinoma. In the present study, an autopsy case of PTTM caused by lung adenocarcinoma is reported and the pathogenesis of this complication is discussed. Multiple nodular lesions in the bilateral lungs were found in a 62-year-old Japanese man. Transbronchial biopsy revealed non-small cell carcinoma. Chemotherapy was performed; however, the patient succumbed to sudden dyspnea. Autopsy revealed poorly differentiated adenocarcinoma with multiple intrapulmonary metastases and intimal proliferation of pulmonary small arteries and arterioles with or without tumor emboli, which were characteristic of PTTM. Tumor cells were immunohistochemically positive for vascular endothelial growth factor (VEGF) and osteopontin (OPN), which are endothelial proliferative factors. This case indicates the possible involvement of VEGF and OPN in the pathogenesis of PTTM caused by lung adenocarcinoma.

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