Fig. 7
Histological findings of the resected specimen. a (10 ×) The epithelium comprises a multilayered columnar epithelium at the pedicle and multilayered squamous epithelium at the apex. A layer of cartilage formed an inverted U-shape in the stroma. Structures mimicking bronchial glands are observed. b (100 ×) Immunostaining showed a selected population of cells positive for TTF-1 (shown in brown), a marker for bronchial epithelium, at the epithelia of the pedicle. c (100 ×) Diffuse staining of MUC4 (shown in brown) is noted in all layers of the stratified squamous epithelium at the apex, which resembled squamous metaplasia of the bronchial epithelia