Besides testicular tumours, so far the expression of the human homologue of the Piwi gene has only been investigated in leukaemia cell lines (Sharma et al, 2001), gastric cancer (Liu et al, 2006) and soft-tissue sarcomas (Taubert et al, 2007a, 2007b), demonstrating elevated protein and/or mRNA transcript levels in the two latter kinds of tumours. This evidence concerns the gene PIWIL4 and soft tissue sarcoma.