空洞性病変を呈した細気管支肺胞上皮癌の1切除例

A Case of Mucinous Bronchioloalveolar Carcinoma Presenting a Pulmonary Cavitary Lesion

要旨　患者は61歳，喫煙男性．右下葉に空洞を伴う浸潤影を認め，精査の結果，高分化型腺癌と診断し(cT2N0M0 stage IB)，右中下葉切除術を施行した．切除標本にて，腫瘍細胞は空洞壁を肺胞上皮置換性に増殖し細気管支へ連なっており，空洞内腔に壊死物や炎症所見は認められなかった．以上より腫瘍細胞が細気管支壁に増殖進展することによって気道が狭小化してcheck valveとなり，末梢の気腔が増大した結果，空洞性病変を示したと考えられた．一方，間質や脈管への腫瘍細胞の浸潤も認められたことから，最終的に粘液産生型気管支肺胞上皮癌を主体とした混合型腺癌と診断した．細気管支肺胞上皮癌は，肺胞性陰影を呈することが一般的であるが，本症例のように空洞性病変を呈した報告も散見される．したがって，細気管支肺胞上皮も鑑別疾患の一つとして考える必要があろう．

　A 61-year-old smoking male sought medical attention because of a persistent dry cough. Radiological studies revealed a cavitary massive lesion in the right lower lobe, which was diagnosed by endoscopic lung biopsy as a well-differentiated adenocarcinoma. A right lower and middle lobectomy was performed as a curative treatment for the patient. Pathological studies of the resected lung demonstrated that the mucinous well-differentiated papillary adenocarcinoma had replaced the epithelia on the inner surface of the cavity. There was no evidence of tissue necrosis or infections within the cavity, suggesting that the cavity was formed by one-way “check-valve” air-traffic through conducting airways which were narrowed by infiltration and multiplication of cancer cells. It was considered to be responsible for the formation of the cavity. Although bronchioloalveolar carcinoma(BAC)is often characterized by its radiological presentation of ground-glass opacity or pneumonic consolidation, the present case and some other reported cases illustrate that BAC may form a cavity and should not be excluded from the differential diagnoses for patients with cavity lesions of the lungs.