Numerous studies have demonstrated that METTL1 is upregulated in a variety of malignancies, including lung cancer, hepatocellular carcinoma (HCC), colorectal cancer (CRC), acute myeloid leukemia (AML), gastric cancer, and breast cancer, and its high expression is often associated with poor patient prognosis (Figure 2). This evidence concerns the gene METTL1 and breast cancer.