KRT20 and breast cancer: In a most recent classification by Lopez-Beltran and colleagues (2021), three subtypes of BC were identified using a Nano String-based four-gene panel expression analysis on a series of 91 BC cases, both NMIBC and MIBC, with classical and subtype histology [26]: luminal subtype (KRT20+/GATA3+), basal subtype (KRT5+/KRT14+/GATA3low/−/KRT20low/−), and null/double negative (non-luminal/non-basal) subtype (KRT14−/KRT5−/GATA3−/KRT20−).