Lactate participation in tumorigenesis is well documented and its role as a metabolic marker and therapeutic target has been explored, with most reports focused on the role of LDHA in breast cancer resistance to treatment, and few focused on LDHB. In this study, we report the potential involvement of lactate dehydrogenase B in breast cancer resistance to treatment that could provide a molecular marker to detect early resistance to tamoxifen among patients. The gene discussed is LDHA; the disease is breast carcinoma.