The earliest classification developed by the Lund University by Lindgren et al. comprised two molecular subgroups of BC: MS1, which included pTa tumors, enriched with FGFR3 mutations (55% in MS1 vs. 7% in MS2, p < 0.05); MS2, which included high-grade tumors and those where TP53 mutations were more common [64]. Here, FGFR3 is linked to breast cancer.