Ross and coworkers have analyzed the most frequent copy number alterations that were observed in mucinous breast cancers and showed that: FGFR1 was more frequently amplified in mucinous than non-mucinous ER+ breast cancer (36% vs 11%); the FGF3/FGF4/FGF19 amplicon was frequently amplified (27%) [226]. Here, FGFR1 is linked to breast cancer.