PIWIL1 and breast cancer: Moreover, an induced expression of PIWIL1 has been linked to lymph node metastasis in patients with gastric cancer (Wang et al., 2012; Gao et al., 2018), colon cancer (Sun et al., 2017), hepatocellular carcinoma (Jiang et al., 2011; Zhao et al., 2012), breast cancer (Wang D.W. et al., 2014), bladder cancer (Eckstein et al., 2018), renal cell carcinoma (Stöhr et al., 2019), and endometrial cancer (Chen et al., 2015a).