[Bronchiolar adenoma: a clinicopathological analysis of 15 cases].

To study the clinicopathological characteristics, diagnosis and differential diagnosis of bronchiolar adenoma (BA). Fifteen cases of BA were collected from the First Affiliated Hospital of Nanjing Medical University, from January 2016 to October 2019. The clinical data, imaging examination, morphology, immunostaining and molecular changes were retrospectively analyzed. There were 3 males, 12 females, most of the patients were female, mainly in middle-aged to elderly (51-77 years). Three had smoking history. The patients usually had no clinical symptoms. Imaging findings were ground-glass and/or lobulated nodules. Grossly, the tumors were gray-whitish, taupe solid or focally microcystic nodules with distinct boundary but no capsule. The maximum diameter was 0.4-2.5 cm (mean 1.0 cm). Histologically, there were glandular, papillary, or flat patterns that were composed of basal cells, mucous cells, ciliated cells and type Ⅱ pneumocytes, some of which showed basal cell proliferation and squamous cell metaplasia. However, there were some cases with few or even without mucous and/or ciliated cells. Immunostaining highlighted the continuous basal cell layer (positive for p63, p40 and cytokeratin 5/6), which was the most important diagnostic evidence. Genetic tests did not show mutation in BRAF or EGFR genes. All patients were followed up for 1-41 months, and they were without recurrence or metastasis. BA is a benign neoplasm that develops in the peripheral lung with good prognosis. Definite diagnosis is very crucial for surgical treatment, especially in frozen consultation. Immunohistochemistry will be helpful if necessary.