Abstract
Background. Bronchiolar adenoma/ciliated muconodular papillary tumor (BA/CMPT) is a nodular lesion that occurs in the peripheral lung and exhibits a bilayer structure of ciliated cells and goblet cells with basal cells. It was added as a benign lung tumor to the 5th edition of the WHO classification in 2021. It has both benign and malignant characteristics, and its classification has been debated. We herein report our experience with a case of BA/CMPT that was difficult to differentiate from squamous cell carcinoma. Case. The patient was a 74-year-old woman. In April 2021, she visited the hospital with a diagnosis of bronchial asthma and diffuse panbronchiolitis (DPB). Erythromycin was administered for DPB, and the scattered granular shadows in the middle lobe lingual segment and both lower lobes on CT improved, while the left lung S6 peripheral nodular shadows remained. After that, the nodule gradually increased in size, and thoracoscopic lower lobe wedge resection of the left lung was performed in May 2023 on suspicion of lung cancer. An intraoperative frozen section examination revealed that part of the nodular lesion just below the S6 pleura was highly atypical, strongly suggesting squamous cell carcinoma. The patient was finally diagnosed with BA/CMPT based on a postoperative pathological diagnosis. Conclusion. To standardize the treatment of BA/CMPT, it is desirable to accumulate reports on histological images, genetic mutations, and treatment results.
