症例は66歳,男性.慢性閉塞性肺疾患とい草塵肺で経過観察をしていた.6カ月前の胸部CTでは明らかな異常を認めなかったが,新たに左上葉の気腫性病変周囲に腫瘤性病変を認めた.気管支鏡検査にて,局所検体からM.avium が検出されたものの生検で肉芽腫病変を認めなかったため,CTガイド下肺生検を実施した結果,肺MAC症と最終診断した.近年,孤立性腫瘤形成型肺MAC症の症例を散見するようになってきているが,本症例のごとく短期間で急速に増大することもあることから,抗酸菌を含めた肺感染症に対する積極的な検査が必要と思われる.A 66-year-old man was admitted to our hospital for follow-up on chronic obstructive pulmonary disease with a recent-showing abnormal chest shadow. He had received a periodic chest computed tomography (CT) six months prior due to a past history of COPD and Igusa pneumoconiosis. Although there was no mass shadow on the chest CT six months ago, a solitary tumorous shadow appeared surrounding the emphysematous lesions in the left upper lobe. M. avium was detected from local specimens viabronchoscopic examination, but because a granulomatous lesion was not observed, we performed a CT-guided lung biopsy and made a final diagnosis of pulmonary MAC disease. We recently observed that pulmonary MAC disease presents as a solitary tumorous shadow. However, as there are cases of pulmonary MAC disease presenting as a rapidly growing tumorous shadow within a short time, it is necessary to perform aggressive examinations for infectious diseases including an acid-fast bacilli examination
