In two studies from the same group [21, 22] it was shown that a CXCL12 gradient was able to stimulate migration of germ cell tumor cells [22], and that non-seminoma stage I patients on surveillance with higher CXCL12 immunoexpression in tumor cells exhibited significantly better relapse-free survival, independently of vascular invasion status [21]. The gene discussed is CXCL12; the disease is testicular germ cell tumor.