Invasive Mucinous Adenocarcinoma
High magnification view showing papillary and lepidic growth patterns in an invasive mucinous adenocarcinoma of the lung. The tumor cells are an admixture of goblet cells and tall columnar cells with intracellular mucin. The alveolar spaces contain abundant mucin. Immunohistochemically, invasive mucinous adenocarcinoma of the lung is positive for CK7 and CK20 and usually negative for TTF1 and Napsin A.