The human genome encodes four PIWIL genes, known as PIWIL1 (HIWI), PIWIL2 (HILI), PIWIL3 (HIWI3), and PIWIL4 (HIWI2); some of which were found to be highly expressed in several human cancers [92,93,94,95,96]. This evidence concerns the gene PIWIL3 and cancer.