FGFR3 and in situ carcinoma: At diagnosis, about 70% of all BCs are low grade (LG) BCs (Ta/pT1/CIS), typically non-invasive tumors, growing as superficial papillary protrusions, genetically associated to FGFR3 mutations and characterized with a high risk of recurrence but low propensity to progress to high grade (HG), invade and metastasize.