Subgroup analysis based on BC subtypes, histological subtypes, stages, and lymph node metastasis showed that the expression of HTR4 decreased in different types of BC tissues compared with normal tissues, and the higher the cancer stage and lymph node metastasis, the lower the expression of HTR4 (Figures 5(b)–5(f)). The gene discussed is HTR4; the disease is metastatic malignant neoplasm in the lymph nodes.