So the IHC staining for TTF-1, CK20, CK7 and Tg were performed on the two tumor specimens(Figure 2), which revealed negative immunoreactivity of CK20, Tg but positive of CK7, TTF-1 in the tumor removed from the lung; while positive immunoreactivity of CK7, TTF-1, Tg but negative of CK20 in the tumor removed from the thyroid. Here, KRT20 is linked to neoplasm.