Further, DNA2 expression was increased in the ER-negative group, PR-negative group, HER2-positive group, and high-grade group via analyzing 2,509 breast cancers in “cBioportal” and 3,063 breast cancer data in “bc-GenExMiner.” Besides, the immunohistochemical staining in 26 breast cancer tissues also showed that elevated expression of DNA2 was correlated with ER-/PR-/HER+. This evidence concerns the gene ESR1 and breast cancer.