In human cancers, some components of the PIWI biogenesis machinery have been characterized24, 37; but tumour specific expression of piRNAs are limited to either single gene studies38, 39, or expression profiles of a few representative tumours40, 41, 42 or cell lines42, 43, 44, 45 for a few types of cancers. Here, PIWIL1 is linked to cancer.