There is a trend of younger breast cancer in China, with younger breast cancer patients accounting for a higher proportion of all patients in China compared to Western countries, with 12% of patients <40 years old in China compared to 6.2% of patients <40 years old in the United States. Guidelines in Europe and the United States usually define young breast cancer as breast cancer patients <40 years of age, while the 2019 Chinese "Expert Consensus on the Management of Young Breast Cancer Diagnosis and Fertility" defines young breast cancer as breast cancer patients with an age of onset ≤35 years. Age is an independent risk factor for increased risk of recurrence and death, and young breast cancer has higher demands on quality of life and fertility needs, so treatment of young breast cancer should be more cautious. For young breast cancer patients, breast-conserving surgery should be the first choice, combined with tumor repair techniques, to ensure the best postoperative appearance. If breast conservation is not available, mastectomy combined with prosthetic reconstruction may also be an option. For patients with BRCA mutation, breast conservation needs to be more cautious, as BRCA mutation does not increase the incidence of ipsilateral recurrence, but increases the incidence of second malignancy and new tumors. Chemotherapy for young breast cancer Is it true that young breast cancer patients should receive stronger chemotherapy regimens with longer cycles? Youngness is an important reference factor for chemotherapy, but not the only basis. The development of chemotherapy regimen needs to be based on the molecular staging of the patient, staging combined with the patient's age and comorbidities. Endocrine therapy for young breast cancer Important considerations for intensive endocrine therapy include the presence of lymph node metastasis and age ≤35 years. Young breast cancer patients should consider intensive endocrine therapy with ovarian suppression (OFS) in combination with tamoxifen (TAM) or aromatase inhibitors (AI), with age <35 years being the absolute beneficiary of OFS in combination with AI. Fertility management in young breast cancer A significant proportion of young breast cancer patients have a desire to have children after treatment. Since chemotherapy increases the chance of premature ovarian failure, patients with fertility requirements should inform their physicians prior to treatment if they will be given ovarian function protection with chemotherapy. Current modalities used for ovarian function protection include: embryo freezing, oocyte freezing, ovarian tissue freezing, and the use of GnRHa. The use of GnRHa, although not absolutely guaranteed to preserve ovarian function, is the easiest and most widely used in clinical practice. The timing of fertility in young breast cancer patients is recommended to be at least 3 years after breast cancer surgery; if positive lymph nodes are present, it is recommended to consider fertility 5 years after surgery. Patients who are taking endocrine therapy drugs need to stop taking them for 6 months before preparing for pregnancy, and endocrine therapy should be continued after the end of childbirth.