Three strains of ascites tumor cells were injected into the cecal lymph follicles of a group of Donryu rats to study the spread of cancer within the lymphatic system. In no case did tumor cells spread beyond the lymph nodes until the third day after inoculation, at which time viable tumor cells appeared within the thoracic duct. In a group of rats in which all the regional lymph nodes were excised prior to tumor inoculation, tumor cells appeared within the thoracic duct immediately after cecal inoculation. Apparently the lymph nodes serve as barriers to the early spread of cancer cells in the lymphatic system. The time required for tumor cells to appear in the thoracic lymph corresponded with the beginning of tumor growth in the regional lymph nodes.
Abe R, Taneichi N. Lymphatic Metastasis in Experimental Cecal CancerEffectiveness of Lymph Nodes as Barriers to the Spread of Tumor Cells. Arch Surg. 1972;104(1):95-98. doi:10.1001/archsurg.1972.04180010089023