審査胸腔鏡にて診断した偽中皮腫性肺癌(pseudomesotheliomatous carcinoma of the lung)の1例

A Case of Pseudomesotheliomatous Carcinoma of the Lung

要旨　患者は肺野病変がなく，胸水細胞診にて腺癌細胞が確認された65歳，男性．化学療法(paclitaxel+carboplatin)を施行中，右胸水多量貯留にて緊急入院となった．胸水ドレナージ後のCTで右肺虚脱，縦隔胸膜を含む広範囲な臓側胸膜肥厚を認めた．その後，審査胸腔鏡検査を施行し，壁側胸膜には白色～ピンク色の不整な結節状病変を多数認めた．病理学的に腺癌細胞を認め，免疫組織化学的染色では，CEA(+)，thyroid transcription factor-1(TTF-1)(+)，calretinin(-)，D2-40(-)であり，悪性胸膜中皮腫は否定的であった．臨床経過を併せ考え，偽中皮腫性肺癌(pseudomesotheliomatous carcinoma of the lung;PMCL)と診断した．PMCLは稀な末梢型肺癌の一型であるため，文献的報告を加えて報告する．

　Pseudomesotheliomatous carcinoma of the lung(PMCL)is characterized by marked pleural extension resembling malignant mesothelioma, and has been confirmed histologically as a peripheral lung cancer. We report a rare case of PMCL in a 65-year-old man. The patient had complained of dyspnea and a chest roentgenogram showed right massive pleural effusion. He had histories of smoking and asbestos exposure. Computed tomography(CT)of the chest revealed diffuse irregular pleural thickening. Pleural tissue sampling was performed by video-assisted thoracoscopic surgery(VATS)using a semirigid thoracoscope. At the operation, tumor was found to have spread along the right pleural surface, which was irregularly thickened. Histochemically and immunohistochemically, the tumor was composed of adenocarcinoma cells positive for CEA and TTF-1, but negative for calretinin, so we finally diagnosed PMCL. In this case chemotherapy using paclitaxel and carboplatin was largely effective. We considered that histological examination is needed for a diagnosis of PMCL in a case of malignant pleural effusion with pleural thickness, and that VATS is probably the best option for this purpose.