Annexin A2 Expression in Aerogenous Metastasis of PulmonaryInvasive Mucinous Adenocarcinoma: A Case Report includingImmunohistochemical Analysis

Aerogenous metastasis (AM) is a form of lung cancer that spreads in a unique fashion, but its mechanisms are still unclear. AnnexinA2 (ANX A2), a membrane-binding protein, promotes cancer invasion and is involved in cell adhesion and polarity. Therelationship between ANX A2 and cancers with poor stromal invasion capacity has not been studied. Weimmunohistochemically analyzed ANX A2 expression in AM observed in a patient with pulmonary invasive mucinousadenocarcinoma. In the primary site, ANX A2 immunopositivity on the cell-cell borders weakened as tumor cells projected andseparated into alveolar spaces. In AM, tumor cell aggregates with ANX A2 immunopositivity near the surface and within thecytoplasm attached to alveolar epithelial cells, then engulfed them and formed a protrusion. As tumor cell aggregates adhered tothe alveolar wall and formed a single layer, cytoplasmic ANX A2-positive products accumulated in the lateral sides of the tumorcells and exhibited distinct membranous positivity. These results indicated that ANX A2 near the tumor cell surface was relatedto alveolar wall attachment. Furthermore, the translocation of cytoplasmic ANX A2 to cell-cell borders changed cellmorphology, adhesion, and polarity restoration.