KRT5 and neoplasm: The high gene expression of KRT5 was presumably due to expression in the normal bronchial epithelium including columnar and basal cells and squamous metaplasia surrounding the tumor, which was evident when reviewing hematoxylin and KRT5 (CK5) IHC stains (Fig. 3A), as these areas were included in the whole sections taken from the tissue block for RNA extraction.