CCL21 and neoplasm: HEVs found in human and mouse tumors, whether associated with TLSs or not, express adhesion molecules and chemokines (e.g. PNAd, MAdCAM1, CCL21, and ICAM1) that may contribute to their interaction with naïve and central memory lymphocytes, facilitating their drainage from the blood and recruitment into tumor tissues (83, 100–103).