Pathological investigation of sentinel lymph nodes

The sentinel lymph-node procedure enables selective targeting of the first draining lymph node, where the initial metastases will form. A negative sen tinel node (SN) predicts the absence of tumour metastases in the other regi onal lymph nodes with high accuracy. This means that in the case of a negat ive SN, regional lymph-node dissection is no longer necessary, Besides savi ng costs, this will prevent many side-effects as a result of lymph-node dis section. The task of the pathologist is to screen SNs for metastases. To th is end, several techniques are available such as standard histo- and cytopa thological techniques, immunohistochemistry, flow cytometry, and molecular biological techniques. These methods are explained and their sensitivity fo r detecting SN metastases is discussed. Some of these techniques also appea r to be useful for intra-operative evaluation of SNs. The standard protocol for detection of SN metastases consists of extensive histopathological inv estigation including step H&E stained sections and immunohistochemistry. In tra-operative frozen-section analysis of SNs has been shown to be reliable for breast-cancer axillary lymph nodes. In the intra-operative setting, imp rint cytology can also be used but its additional value to frozen section a nalysis is not yet clear. Further studies are necessary to establish the ro le of sophisticated molecular biological techniques such as reverse transcr iption polymerase chain reaction (RT-PCR) in detecting SN metastases. The s ensitivity of flow cytometry is too low for this purpose.