Abstract / Summary
Ciliated muconodular papillary tumor (CMPT) is a rare peripheral pulmonary tumor composed of bilayered structures resembling bronchial epithelial and basal cell components. Cases of CMPT coexisting with lung cancer are particularly rare, with only 22 cases reported to date. A Japanese male patient in his 70 s underwent left lower lobectomy for primary lung adenocarcinoma. Two years after the initial surgery, radiological surveillance revealed a newly developed ground-glass opacity in the right lower lobe. This finding prompted a subsequent segmentectomy involving superior and posterior basal segment of the right lower lobe. Histopathological examination of the resected sample confirmed papillary adenocarcinoma, with multiple additional nodules histologically diagnosed as CMPT. Notably, CMPT components were observed adjacent to areas of adenocarcinoma within the same surgical sample. Given the presence of multiple nodules and the potential for malignant transformation, a comprehensive genomic analysis was performed. KRAS G12V mutations were found in the adenocarcinoma lesions, but not in the isolated CMPT components. Although CMPT often harbors genetic mutations—most commonly BRAF V600E and EGFR mutations—coexistent CMPT and lung adenocarcinoma rarely share the same driver mutation. However, recent reports suggest that CMPT may undergo malignant transformation or appear adjacent to carcinoma. In this case, no shared mutations were identified between the adenocarcinoma and isolated CMPT lesion. Nonetheless, given the potential for malignant transformation in CMPT, further accumulation and analysis of comprehensive nucleic acid data, including whole-genome and RNA sequencing data with laser-capture microdissection of the samples, are warranted.