Although, all the mechanism(s) by which leptin contributes to tumour progression are unknown, our published data suggest that specific leptin signalling increase cancer-cell proliferation and the expression of VEGF/VEGFR2 in breast (Gonzalez et al, 2006; Rene Gonzalez et al, 2009; Gonzalez-Perez et al, 2010; Guo et al, 2010) and endometrial cancer (Carino et al, 2008), and in endometriotic lesions (Styer et al, 2008). This evidence concerns the gene LEP and cancer.