The present invention describes a method for identification and labeling of sentinel lymph nodes (SLNs) and the presence or absence of lymph node metastases as an important diagnostic and prognostic factor in early stage cancers of all types. The method, know as Molecular Lymphatic Mapping, uses traditional dye/radioactive tracer based techniques in conjunction with a nucleic acid marker to identify and label the SLN, not only for current diagnostic methods, but for archival purposes. In addition, MLM can be used to deliver a therapeutic gene or genes to the SLN to activate tumor immunity to tumor cells, and/or to inhibit tumor metastases. The methods may be combined with therapeutic intervention including chemotherapy and radiotherapy.