NECTIN4 and breast cancer: Even though no large differences between overall NECTIN4 staining and NECTIN4 cell membrane positivity have been observed in non-invasive areas of urothelial HG BC lesions, a prominent discrepancy was present in the stroma-invasive parts of urothelial HG BC samples (96% overall NECTIN4 protein positivity, 51% membranous NECTIN4 positivity) as well as normal urothelial specimens (62% overall protein positivity, 4% membranous NECTIN4 positivity).