대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Bronchiolar Adenoma/Pulmonary Ciliated Muconodular Papillary Tumor

Radiologic Findings

Fig 1-3. A chest CT scan reveals a 15mm-sized cystic nodule in the right upper lobe with eccentric nodular wall thickening, raising suspicion for cystic lung cancer.
Fig 4. The cystic nodule, however, showed no significant changes compared to the chest CT obtained two years ago

Brief Review

Bronchiolar adenoma (BA) or ciliated muconodular papillary tumor (CMPT) is a benign lung tumor categorized in the 5th edition of the World Health Organization (WHO) Classification of Lung Tumors. BA/CMPT predominantly occurs in the peripheral regions of the lungs and presents with a bilayered bronchiolar-type epithelial structure. Histologically, BA shows a bilayered structure with luminal ciliated and/or mucinous cells over a continuous basal cell layer, which is highlighted by p40 or p63 and helps separate BA from adenocarcinoma. It generally does not show malignant behavior, but mutations in genes such as BRAF and EGFR, which are common in lung cancer, raise concerns about potential malignant transformation in some cases.

On CT, BA/CMPT typically appears as a small, peripheral lower‑lobe nodule that can be solid, part‑solid, or pure ground glass and often shows cavitation or pseudo‑cavitation; a “vacuolar sign,” referring to small focal air‑containing lucencies within the nodule, has also been described as a characteristic feature in some lesions. FDG PET usually demonstrates low uptake with SUVmax around or below 2.5, and follow‑up imaging often reveals extremely slow growth, consistent with its indolent nature. The main differential diagnoses are adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), invasive mucinous adenocarcinoma, and infectious or inflammatory nodules. In recent literature, a small peripheral nodule with vacuolar or pseudo‑cavitary lucencies, blurred tumor-lung interface, lower‑lobe predominance, low SUVmax, and very slow growth can help differentiate BA/CMPT from these conditions.

References

1. Liu X, Xu Y, Wang G, Ma X, Lin M, Zuo Y, Li W. Bronchiolar adenoma/ciliated muconodular papillary tumour: advancing clinical, pathological, and imaging insights for future perspectives. Clin Radiol. 2024 Feb;79(2):85-93.
2. Cao L, Wang Z, Gong T, Wang J, Liu J, Jin L, Yuan Q. Discriminating between bronchiolar adenoma, adenocarcinoma in situ and minimally invasive adenocarcinoma of the lung with CT. Diagn Interv Imaging. 2020 Dec;101(12):831-837.
3. Krishnamurthy K, Kochiyil J, Alghamdi S, Poppiti R. Bronchiolar adenomas (BA) - A detailed radio-pathologic analysis of six cases and review of literature. Ann Diagn Pathol. 2021 Dec;55:151837.

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