Fig. 1

Represents the structure of the lymphatic system and tumor cells entering and leaving the draining LNs. a represents the hierarchical structure of lymphatic subtypes. Various cells (including cancer cells and immune cells) derived from the tumor microenvironment enter the LNs with the interstitial fluid passing through the initial lymphatic, the pre-collective lymphatic and the collecting lymphatic in turn. b represents the cancer cells into and out of the drainage LNs. With the interstitial fluid, the cancer cells begin at the blind end of the lymphatic, and then enter the afferent lymphatic, medullary sinus and efferent lymphatic of the draining LNs in turn, and finally the efferent lymphatic become the afferent lymphatic of other LNs