Breast cancer in young women is a complex disease to manage due to its biological heterogeneity and special issues related to toxicity of different treatment strategies. Defining a cut-off for young age has been challenging since it is not clear whether the prognostic effect of age is continuously variable or whether there are certain thresholds at which the prognosis changes (e.g. those < 50 years of age or ≤ 35 years of age). In this review article, we define young patients as those being premenopausal. In addition, we discuss the most recent data of the biological diversity of breast cancer arising in premenopausal patients and current treatment modalities in early and advanced settings. Survivorship, with special emphasis on the importance of early supportive care, is also discussed.