Although several studies have shown no significant differences in survival according to age in hormone receptor–negative breast cancer, it has been reported that hormone receptor–positive breast cancer diagnosed at a younger age has a poorer survival outcome.11,12 Because young patients with hormone receptor–positive, ERBB2-negative breast cancer have a relatively long life expectancy, the cumulative risk of late recurrence after 5 years in younger patients is greater than that of older patients, which should be considered in the treatment of young patients with breast cancer. This evidence concerns the gene ERBB2 and breast cancer.