broadly , the present invention is directed to a method for the detection and differentiation of neoplastic tissue in a patient suspected of having neoplastic tissue . the method includes the administration of a radiolabeled somatostatin congener to the patient and accessing the patient with a radiation detection probe for determining tissue exhibiting elevated levels of radiation , viz ., neoplastic tissue . however , before subjecting the patient to such administration , an initial determination preferably is made as to whether the radiolabeled somatostatin congener will bind to the tumor site , i . e ., whether somatostatin receptors are associated with the neoplastic tissue . this is conveniently done with a wide variety of endocrine tumors , which release peptides or hormones , referred to as &# 34 ; biochemical markers . &# 34 ; in order to make this determination , initially a biochemical marker - inhibiting dose of unlabeled somatostatin congener is administered to the patient . the biochemical marker associated with the neoplastic tissue then is monitored to determine whether the administered somatostatin congener reduces the presence of the marker in the patient . if the monitored presence of the marker was reduced , then the surgeon can be confident that the neoplastic tissue or tumor contains receptors to which the somatostatin will bind . thus , the administration of radiolabeled somatostatin congener is appropriate for such patient . if the biochemical marker associated with the neoplastic tissue is not appropriately reduced following the administration of the unlabeled somatostatin congener , then the neoplastic tissue may not be determinable by the use of radiolabeled somatostatin congener and alternative modalities of treatment should be considered , such as the use of radiolabeled antibodies as proposed in u . s . pat . no . 4 , 782 , 840 . if the tumor is of a type that does not release a biochemical marker , the presence of somatostatin receptors can be confirmed by other means , such as pathology , immunohistochemistry , radioreceptor assay , or such other means as will be apparent to those skilled in the art .