Frequent EGFR exon 20 insertion in the so-called peripheral-type squamous cell neoplasm of uncertain malignant potential: a variant of bronchiolar adenoma or under-recognised entity?

PSCN-UMPs exhibited the proliferation of bland squamous cells accompanied by entrapped pneumocytes and frequent EGFR exon 20 insertions, which showed distinct features from BAs and SCCs. Recognition of this specific entity will help to expand the morphologic and molecular spectrum of peripheral lung squamous neoplasms.