Background and Aims: The incidence rate of breast cancer ranks first among all female malignant tumors, and the prognosis of breast cancer in young women is relatively poor. Young women with breast cancer require special attention because they often face unique physical, psychosocial and emotional issues. This study was conducted to investigate the clinicopathologic characteristics of breast cancer in young adults by analyzing the relevant data of 518 young breast cancer women from a single center in Hunan, so as to provide evidence for optimizing the treatment for this group of patients.  
Methods: The records of 518 women aged ≤35 years with breast cancer undergoing surgical treatment in the Department of Breast Surgery of Xiangya Hospital, Central South University from January 2002 to April 2018 were retrospectively analyzed, and 435 women aged ≥65 year with breast cancer treated during the same period were served as control. The differences in clinical and pathologic features between the two groups of patients were compared. Furthermore, the distribution of molecular subtypes of the 518 patients were compared with those from previous studies in different breast cancer populations.
Results: Among the 518 young breast cancer women, the proportion of cases with age from 31 to 35 accounted for 69.5%, with a normal BMI (18.5–<25 kg/m2) accounted for 74.5%, 18.2% were nullipara, 3.3% had a family history of breast cancer, 63.7% underwent neoadjuvant chemotherapy, 77.03% were subjected to the modified radical mastectomy, 57.0% had a stage TNM II disease, 53.7% were found no lymph node metastasis, 80.5% were invasive ductal carcinomas of no special type, and luminal cancer was the main molecular subtype, with luminal A type accounting for 37.6% and luminal B type accounting for 29.2%. In young breast cancer women versus older breast cancer women, the distribution of molecular subtypes showed no significant difference (P>0.05), the proportion of cases with normal BMI was higher (74.5% vs. 60.9%), the proportion of cases with stage III–IV disease was higher (25.5% vs. 20.5%), the proportion of cases without lymph node metastasis was lower (53.7% vs. 66.2%), both breast-conserving surgery rate and proportion of cases with synchronous reconstructive surgery were higher (9.3% vs. 3.2%; 7.5% vs. 1.8%), and all the differences had statistical significance (all P<0.05). The distribution of molecular subtypes of the 518 patients were significantly different with those from the authors’ previous studies in the overall breast cancer population in Hunan province (both P=0.000), but was similar with those from studies in young breast cancer population in China’s Guangdong province and America (both P>0.05), and the differences occurred in the former was considered due to the changes in detection method and subtyping criteria.
Conclusion: Compared with elderly breast cancer women, young breast cancer women have a relatively rapid disease progression, are more likely to develop lymph node metastasis, and have higher requirements for breast-conserving surgery and breast reconstruction. Therefore, aggressive breast cancer screening to improve the early detection rates is still of great importance. Meanwhile, the breast-conserving rate should be further increased, and the breast reconstruction and fertility preservation technologies should be continuously developed.