PKM and metastatic malignant neoplasm in the lymph nodes: Regarding that Zhu et al only included 2 studies with 591 patients and conclude the overall survival and PFS in their manuscript, we investigated 6 screened individual studies from PubMed, Web of Science, Embase (via Ovid), and Cochrane Library databases with a sum of 895 cases to assess the clinical value including OS, 5-year PFS, T stage, lymph node metastasis, and tumor differentiation of PKM2 in subjects with breast cancer.