Analysis of the tumor characteristics in young age breast cancer patients using collaborative stage data of the Korea Central Cancer Registry

Purpose This study aimed to evaluate tumor characteristics in young age (20–39 years old) breast cancer (YABC) patients in Korea. Materials and methods We identified 10,897 breast cancer patients from 2010 to 2015. The data were collected through 10% systematic sampling of the Korea National Cancer Incidence Database (KNCI DB). Tumor size, lymph node status, estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status were collected according to the Collaborative Stage version 2 (CSv2) Data Collection System. Results Of the 10,897 patients, 1245 (11.4%) were YABC patients. They were found to have larger tumors (T2: 41.6% in 20–39 age group vs 36.4% in 40–49 age group vs 36.5% in 50–59 age group vs 38.4% in ≥ 60 age group; T3: 10.1% vs 7.3% vs 6.5% vs 6.2%, P