Malignant transformation of pulmonary bronchiolar adenoma into mucinous adenocarcinoma: A case report

Figure 4 Immunohistochemical staining of the bronchiole adenoma area. A: CK5/6 (×400); B: p40 (×400); C: CK7 (×400); D: TTF-1 (×400); E: Napsin A (×400); F: Ki-67 (×400). CK5/6 and p40 were expressed continuously in the basal cell layer in some areas, and had a discontinuous skipping pattern in other areas. CK7 had diffuse expression in basal cells and luminal cells. TTF-1 was expressed in basal cells, ciliated cells, and cubic cells, but not mucinous cells. Luminal cells had a patchy weak expression of napsin A. The Ki-67 index was low.