Among 37 YA with hormone receptor positive (HR+) BC, frequent alterations included TP53 (39 %), ESR1 (27 %), PIK3CA (25 %), FGFR3 (18 %), FGFR4 (18 %), FGFR19 (18 %), CCND1 (18 %). Here, FGFR4 is linked to breast cancer.