Postoperative systemic adjuvant therapy (a) Ductal carcinoma (including medullary carcinoma and micropapillary carcinoma), lobular carcinoma, mixed carcinoma, septic carcinoma 1. ER positive and/or PR positive (1) If HER2 positive ①PT1, T2, T3 and PN0 or PN1mi (≤2mm axillary lymph node metastasis): tumor ≤0.5cm or microinfiltration: PN0, consider adjuvant endocrine therapy. PN1mi, adjuvant endocrine therapy or adjuvant chemotherapy combined with trastuzumab therapy with follow-up endocrine therapy; tumor 0.6-1.0cm: adjuvant endocrine therapy ± adjuvant chemotherapy combined with trastuzumab; tumor >1cm: adjuvant endocrine therapy + adjuvant chemotherapy combined with trastuzumab (category 1). (2) Positive lymph nodes (one or more metastases in one or more ipsilateral lymph nodes >2mm): adjuvant endocrine therapy and adjuvant chemotherapy combined with trastuzumab. (2) If HER2 negative ①PT1, T2, T3 and PN0 or PN1mi (≤2mm axillary lymph node metastases) Tumor ≤0.5cm or microinfiltration: PN0, consider adjuvant endocrine therapy (2B); PN1mi (≤2mm axillary lymph node metastases), adjuvant endocrine therapy ± adjuvant chemotherapy (2B); Tumor >0.5cm, consider RT- PCR gene assay, if not done, adjuvant endocrine therapy ± adjuvant chemotherapy (category 1); if low recurrence score, adjuvant endocrine therapy; if moderate recurrence score, adjuvant endocrine therapy ± adjuvant chemotherapy; if high recurrence score, adjuvant endocrine therapy + adjuvant chemotherapy. (ii) Positive lymph nodes (one or more metastases in one or more ipsilateral lymph nodes >2mm): adjuvant endocrine therapy + adjuvant chemotherapy. (II) If pathology is ductal carcinoma and mucinous carcinoma of breast ER positive and/or PR positive 1. PT1, T2, T3 and PN0 or PN1mi (≤2mm axillary lymph node metastasis): tumor <1cm: no adjuvant therapy; tumor 1-2.9cm: consider adjuvant endocrine therapy; tumor ≥3cm, adjuvant endocrine therapy. 2. Positive lymph nodes (one or more metastases in one or more ipsilateral lymph nodes >2mm): adjuvant endocrine therapy ± adjuvant chemotherapy.