Abstract: Objective · To explore and analyze the differences of clinicopathological features and prognosis and influencing factors in young breast cancer patients in different age groups. Methods · A total of 277 female breast cancer patients with invasive ductal carcinoma under 40 years old who were diagnosed and treatedoperation at the International Peace Maternity & Child Health Hospital, Shanghai Jiao Tong University School of Medicine Jan. 2010 to Dec. 2018 were retrospectively analyzed. The patients were divided into two groupsthe age of 35 years old, i.e. aged ≤ 35 group and aged >35 and ≤ 40 group. The differences of clinicopathological features were compared between the two groups, including histological classification of cells, tumor size, lymph node metastasis, estrogen receptor (ER) , progesterone receptor (PR) , human epidermal growth factor receptor-2 (HER2) , the of Ki-67, the degree of intravascular invasion, pathological stage and molecular subtype. The prognostic differences and influencing factors of the two groups were analyzed. Results · There were no significant differences in histological classification of cells, tumor size, lymph node metastasis, ER , PR , HER2 , the of Ki-67, the degree of intravascular invasion, pathological stage and molecular subtype between the two groups. The 3-year disease-free survival (DFS) of the patients in the aged ≤ 35 and >35 and ≤ 40 group were 89.66% and 95.03%, respectively, and there was no significant difference. There was no statistically significant difference in the 3-year DFS among the four molecular subtypes between the two groups. Cox proportional hazards model showed that intravascular invasion and lymph node metastasis were the independent risk factors of DFS. Conclusion · >35 and ≤ 40 year-old breast cancer patients and ≤ 35 year-old breast cancer patients have similar clinicopathological features and prognosis, so the same treatment strategy should be given.

Key words: young patient with breast cancer, clinicopathological feature, prognosis