TTF1 and lung cancer: Immunohistochemical testing shows that tumor cells in infiltrating adenocarcinoma of the lungs are positive for lung cancer-related markers, such as CK7, napsin A, and TTF-1, while PM is negative for these markers.14 The tumor cells in our patient showed no characteristics of adenocarcinoma cells, and immunohistochemistry also ruled out the possibility of lung-infiltrating adenocarcinoma.