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

Figure 5 Immunohistochemical staining of the mucinous adenocarcinoma area. A: CK5/6 (×100); B: p40 (×100); C: CK5/6 (×400); D: p40 (×400); E: CK7 (×400); F: TTF-1 (×400); G: Napsin A (×400); H: Ki-67 (×400). CK5/6 and p40 were present in a clear boundary at the junction between the bronchiole adenoma and mucinous adenocarcinoma (MA) (A-B, yellow dotted line). The basal cell layer in MA area was completely absent, as shown by staining for CK5/6 and p40, suggesting an invasive disease. The tumor cells were strong diffuse positive for CK7; whereas TTF-1 and napsin A showed only patchy positivity, indicating the differentiation of alveolar epithelial type II cells. The Ki-67 index was low in the infiltrating area.