Younger breast cancer patients are less common in Western countries, but represent a higher percentage of breast cancer patients in China. The definition of “young” generally refers to 30, 35 or 40 years old or younger, but most people define 35 years old or younger as “young”. According to foreign data, the incidence of breast cancer in women under 35 years old is only 1.9%, while according to our data, breast cancer under 30 years old accounts for 2.6% of breast cancer admissions in the same period. Tumor epidemiological studies have found that breast cancer in Eastern populations is characterized by an earlier age of onset than in Western populations. The biological behavior of younger breast cancer patients and the risk of recurrence of breast cancer in patients are different from those of older patients, which leads to different treatment strategies for these two groups. Clinical, pathological and biological characteristics Younger breast cancer patients have the following characteristics: (1) more advanced stage than older patients, and even if they have the same stage, the prognosis of younger patients is worse, which is caused by the different biological behaviors of the two groups; (2) more prone to bone marrow micrometastases; (3) most of them are invasive carcinomas, and about 70% are invasive ductal carcinomas; (4) tumor cells are highly malignant, and most of them have vascular aneurysm emboli, extensive intraductal carcinoma component, human surface (4) The tumor cells are highly malignant, and most of them have features such as vascular neoplasm thrombus, extensive intraductal cancer components, overexpression of human epidermal growth factor receptor 2 (HER2) (positive rate of 26%-44%), negative estrogen receptor (ER) (negative rate of 39%-80%), high proportion of S-stage cells, and overexpression of P53 and Ki-67; (5) Basal-like breast cancer or triple-negative breast cancer is common, among breast cancer patients under 30 years old, 34% are basal-like breast cancer, and the overall incidence of basal-like breast cancer is 14% to 16%. Treatment strategies Surgery Because younger patients may have more invasive histologic features (extensive intraductal cancer component, poor cellular grading, with choroidal aneurysm emboli) and a higher incidence of positive margins, it is generally believed that younger patients have a higher rate of local recurrence (LR) after breast-conserving surgical treatment (BCT) than older patients. However, there is controversy regarding the effect of age on local recurrence. There is evidence that improvements in treatment may reduce LR rates in younger patients who undergo BCT. One study showed that the LR rates in patients under 35 years of age with positive, indeterminate, and negative cut margins were 50%, 33.3%, and 20.8%, respectively. This strongly suggests that the cut margin status of younger patients must be handled more carefully. Another randomized study showed that local dosing with radiotherapy reduced the 5-year LR rate from 19.5% to 10.2% in patients <49 years of age. Similarly, tamoxifen (TAM) reduced the risk of LR by 38% in patients <49 years of age with ductal carcinoma in situ, compared with only a 22% reduction in patients >50 years of age. There is no evidence yet that overall survival (OS) rates are reduced in younger patients receiving BCT. Definitive findings on the effect of age on LR after radical surgery are still lacking. Negative cut margins, application of local add-on to radiotherapy and adjuvant systemic therapy all reduce the risk of LR in young patients after BCT. Youth is not a contraindication to BCT. Internal therapy Adjuvant chemotherapy is effective in reducing the risk of recurrence in patients <50 years of age. This is partly due to the higher proportion of ER-negative patients in younger patients and the different biological behavior of their tumors from older patients. Preoperative chemotherapy in younger patients may reduce disease staging and make them more suitable for BCT and save them from aesthetically compromising radical surgery. However, there are no reports of improved survival with neoadjuvant chemotherapy. Oral TAM for 5 years is the standard of care for premenopausal patients with hormone receptor-positive early-stage breast cancer. Aromatase inhibitors are not indicated for the treatment of premenopausal breast cancer. Ovarian debulking may also be an effective treatment. Ovariectomy and radiation therapy may be used as well as luteinizing hormone-releasing hormone (LHRH) analogs to achieve reversible pharmacologic debulking. A meta-analysis by the Early Breast Cancer Clinical Trials Collaborative Group (EBCTCG) confirmed that patients <50 years of age can benefit from ovarian debulking therapy alone. In addition, the results of several randomized studies illustrate that ovarian denervation ± TAM, has similar efficacy to cyclophosphamide + methotrexate + 5-fluorouracil (CMF) chemotherapy. An expert consensus from St. Gallen suggests that ovarian denervation combined with TAM may be used as adjuvant therapy in selected premenopausal patients with a moderate risk of recurrence. A clinical study found that treatment with CAF+TAM+goserelin significantly improved prognosis compared with cyclophosphamide+doxorubicin+5-fluorouracil (CAF) chemotherapy+goserelin (5-year recurrence-free survival rates of 78% and 67%, respectively). Treatment strategies for breast cancer during pregnancy and lactation Breast cancer during pregnancy and lactation (i.e., pregnancy-related breast cancer) is defined as breast cancer diagnosed during pregnancy or within 1 year after delivery, and its incidence ranges from 0.2% to 3.8% of all breast cancers. 70% of breast cancers during pregnancy and lactation occur in patients under 30 years of age. We have retrospectively analyzed the clinical data of 129 breast cancer patients under 30 years of age admitted to our hospital from January 1980 to May 2000, and breast cancer during pregnancy and lactation accounted for 24.8%, which is similar to domestic and international reports. Invasive ductal carcinoma is the most common pathological type of breast cancer during pregnancy and lactation. Most patients have poorly differentiated tumors and are often associated with choroidal aneurysm emboli. The prognosis of patients with breast cancer during pregnancy and lactation is generally considered to be poor. However, Nugent et al. reported a 5-year survival rate of 57% in patients with breast cancer during pregnancy and 56% in patients without breast cancer during pregnancy and lactation, with no significant difference. In addition, Daling et al. found that the prognosis of patients who had children within 2 years before the diagnosis of breast cancer was inferior to that of patients who did not have children within 5 years before the diagnosis. This may be due to the reduced immune surveillance capacity of the former and the increased hormone levels during pregnancy. The degeneration of breast tissue due to the inflammatory state prior to pregnancy and lactation may explain the higher rate of metastasis in this group of patients. In the aforementioned retrospective study, after comparing the survival of (non)pregnant lactating breast cancer, the investigators also did not see any significant difference according to clinical stage and axillary lymph node status. Therefore, we believe that the prognosis of breast cancer in pregnancy and lactation may not be poor as long as the stage is the same as that of non-pregnancy and lactation breast cancer and the patient has received regular comprehensive treatment. Patients with gestational lactating breast cancer may require chemotherapy during pregnancy, but alkylating agents should be avoided because of their serious teratogenic effects and high miscarriage rate. Anthracycline-based combination chemotherapy regimens may be used in these patients because they are less harmful to the fetus. Foreign scholars have reported a low incidence of chemotherapy complications in 52 children whose mothers were treated with CAF during pregnancy, and the children were healthy and did well in school. However, even if this is the case, the decision to continue the pregnancy, the need for chemotherapy, and the timing of chemotherapy should be made after full communication with the patient and weighing the pros and cons. Summary Breast cancer in younger patients is more aggressive and has a poorer prognosis. Younger patients who undergo breast-conserving surgery may have a higher rate of local recurrence compared to older patients. Life expectancy, fertility issues, and the risk of premature ovarian failure due to chemotherapy are unique concerns that should be addressed in young breast cancer patients. Therefore, careful assessment of the physical and tumor status of young breast cancer patients prior to treatment, development of a rational treatment strategy, and more attention to the psychosocial issues of this group of patients will undoubtedly help to improve their outcomes.