Bronchiolar adenoma with squamous metaplasia: a distinct phenotype

Abstract

We discovered a distinct subtype of pulmonary bronchiolar adenoma termed bronchiolar adenoma with squamous metaplasia. It is composed of columnar surface cells, basal cells, and sheet-like spindle-oval cells with squamous metaplasia in the stroma. All five samples harboured the BRAF V600E mutation. Importantly, BASM may be misdiagnosed as pulmonary sclerosing pneumocytoma upon frozen sections analysis. It may need further immunohistochemistry staining.