[A case of adenocarcinoma of the lung with a pulmonary thromboembolism which improved with gefitinib].

A 56-year-old man was admitted, and was given a diagnosis of adenocarcinoma of the lung (T2N0M0, clinical stage IB), but pleural dissemination was found during surgery. A computed tomography (CT) scan 10 months after surgery revealed enlargement of the mediastinal lymph nodes and a thrombus in the pulmonary artery. Although the patient was immediately given warfarin and heparin, the warfarin was discontinued due to liver dysfunction, and the thromboembolism in his pulmonary artery recurred. The epidermal growth factor receptor (EGFR) mutation investigation of the surgical specimen revealed an EGFR point mutation at exon 21 (L858R). Gefitinib treatment was started and his levels of plasma D-dimer immediately decreased. The mediastinal lymph nodes shrank, and the thrombus in the pulmonary artery had disappeared on a CT scan 2 months after gefitinib treatment. Tumor regression was observed, and no recurrence of the pulmonary embolism was found 10 months after gefitinib treatment. Gefitinib was therefore a very effective treatment not only for lung cancer, but also for pulmonary embolism due to lung cancer.