Involvement of RLN by tumor cells is a prognostic index of survival and a biologic indicator of more distant metastatic disease. In most solid tumors in humans, removing the draining lymph nodes seems to have little impact on survival, although it may be important in local control of disease. Although data from animal studies suggest that tumor draining RLN may have an important antitumor role (particularly in the early stage of tumor growth), there is a shortage of evidence in humans to substantiate such a supposition. At the time of operation, alterations in nodal microarchitecture with an expansion of T and B lymphocyte compartments is well documented. The findings of immunologic studies, however, reveal a general hyporeactivity, inappropriate humoral and cell mediated responses to antigens associated with tumors and a low or absent natural cytotoxicity. Failure of host defenses, possibly induced by tumors, may be responsible for progressive growth of tumor and spread of tumor to the RLN, resulting in dissemination of the tumor cells, establishment of metastatic deposits and concurrent growth of tumor in lymph nodes. Regional lymphatics may have an important antitumor role at the early stage of the development of a tumor (as yet unproved in humans). With progressive growth of tumor, the lymphatics are unlikely to be beneficial, not only because of a failure of nodal anticancer defenses, but because they provide a possible preferred biologic environment for tumor cell proliferation and an anatomic route for dissemination to distant tissues and organs.