The present invention is directed to instruments and instrumental techniques for locating cancer cells in lymph nodes which utilize a radiation detector operatively connected to an ultrasound probe for locating the exact position of radiation tagged tissue, particularly in sentinel lymph nodes followed by placement of a biopsy device. Also described are unique new interoperative radiation detection probes for use in these techniques which include structure for placement of a biopsy device or biopsy needle into the located lymph node and procedures for removal of small portions of detected radiation emitting sentinel lymph nodes for evaluation in a pathology laboratory by measurement of expressed genes located in the removed tissue. The instruments and instrumental techniques also facilitate the subsequent delivery of materials to reverse the unfavorable immune response or environment conducive for metastasis in the sentinel lymph node once cancer cells are located therein.