肺空洞性結節を呈したBA/CMPTの1例

A case of bronchiolar adenoma/ciliated muconodular papillary tumor（BA/CMPT）presenting as a cavitary pulmonary nodule

bronchiolar adenoma/ciliated muconodular papillary tumor（BA/CMPT）は2002年に石川によって提唱され^1），WHO第5版から記載されたまれな組織型の肺腫瘍であり，典型的にはサイズの小さい充実性結節やすりガラス結節を呈することが知られている。今回我々は，空洞性結節を呈したBA/CMPTの1例を経験したので病理所見と対比して報告する。

Bronchiolar adenoma/ciliated muconodular papillary tumor（BA/CMPT）is a rare benign pulmonary epithelial neoplasm that typically presents as a small solid or ground-glass nodule. We report a case of BA/CMPT in a woman in her 50s who presented with a cavitary nodule in the left lower lobe, identified incidentally during evaluation as a living kidney donor candidate. CT revealed a 16-mm cavitary nodule with spiculation and pleural indentation in segment 8 of the left lung, showing no interval change at 3-month follow-up. FDG-PET/CT demonstrated no abnormal uptake. The lesion was resected by video-assisted thoracoscopic surgery for diagnostic purposes. Histopathological examination revealed dilated bronchioles with abundant extracellular mucin production and bilayered proliferation of ciliated columnar epithelium and basal cells, consistent with BA/CMPT proximal type. The cavity formation was considered to reflect cystic dilatation of bronchioles due to a check-valve mechanism. This case highlights that BA/CMPT can present as a cavitary nodule, which should be included in the differential diagnosis of cavitary lung lesions.