PIWIL4 and neoplasm: PIWIL1, PIWIL2, PIWIL3 and PIWIL4 were all deregulated with a dissociated profile: PIWIL1 and PIWIL3 had an abnormal emergent expression and the remaining PIWIL2 and PIWIL4 were variably downregulated in tumor tissues at RNA and protein levels (Figure 1).