Breast cancer 21-gene test includes 16 tumor-related genes and 5 reference genes. According to the test results, recurrence score value (high, medium, low) is obtained, which is important for predicting prognosis, recurrence, metastasis, and guiding the treatment. Especially, it is of great significance in judging the need of chemotherapy for the first-time treatment of patients with stage 1, 2, lymph node (-), hormone receptor (+), and premenopausal or for the elderly patients with postmenopausal, lymph node (+), and estrogen receptor (+).