S100P and lung adenocarcinoma: The use of a limited immunohistochemical panel including napsin A, a recently described highly sensitive marker for lung adenocarcinoma, and GATA3 and S100P, two novel markers of urothelial differentiation, has also been reported to be very useful in differentiating lung adenocarcinoma metastatic to the bladder from primary bladder adenocarcinoma [4].