Previous reports have shown that chemokines are critical for the infiltration and egress of immune cells from tumours, including the CXCR4-CXCL12 axis shown in mouse models of melanoma33, as well as a pre-requisite for the formation of TLSs, including the CXCR5-CXCL13 axis34. The gene discussed is CXCR4; the disease is neoplasm.