TTF1 and cholangiocarcinoma: As a commonly used IHC marker, TTF-1 is usually expressed in LUAD, and its expression may decrease accompanied with disease progression, while Napsin A is expressed in approximately 70%–90% of LUAD tissues, but it is also expressed in a variety of tumors such as renal cancer, ovarian cancer, cholangiocarcinoma, etc. CK7 has a high sensitivity but relatively low specificity.