Improved Inspection Of Regional Lymph Node And Micrometastasis With MLNRS Combining CK20 In Gastric Carcinoma

ObjectiveGastric carcinoma is the most common gastrointestinal tumor in China, with lymphatic metastasis as its main metastasis route. In patients with gastric carcinoma who underwent radical gastrectomy, 70% of them were found positive in lymph node for metastasis. According to the TNM classification of UICC (1997) , Nx denotes the regional lymph node cannot be evaluated ;N, indicates that 1 to 6 lymph nodes are found positive for metastasis ;N₂,7 to 15 and N₃, more than 15. Increasing in the number of examined lymph nodes or more slices per lymph node would increase the detection of positive lymph nodes for metastasis and possibly upstage the N classification. This would help us to assess the staging, treatment and prognosis of gastric carcinoma.Modified lymph node revealing solution ( MLNRS) is prepared with an-hydrate alcohol, diethyl ether, turpentine, acetic acid, 10% buffered formaldehyde and certain amount of methyl blue. MLNRS is mainly applied in identification of positive lymph nodes in various tumor specimens. In practice, MLNRS can improve the accuracy concerning the detection of lymph node metastases. CK20 is confined only to gastrointestinal epithelium and cannot be expressed in normal lymphatic tissue, blood, or bone marrow. Detection of CK20 in non -epithelium indicates the presence of tumor cells. Such defects as incomplete lymph node detection and missing of micrometasatsis of tumor with routine HE staining could not be solved by traditional method. In this study, MLNRS was applied combined with CK20 immunohistochemical method to examine the regional lymph node, in order to find an efficient, accurate and valuable methodfor lymph node detection.Methods46 specimens after standardized D2 gastrectomy in China Medical Universitywere chosen prospectively for study.Regional lymph nodes were examined firstly by conventional method for positive ones and then underwent routine pathological examination. Non - fixed, the entire surgical specimen was searched for lymph nodes with palpation and visualization by experienced clinician and further by the researcher.The surgical specimen which were treated by conventional method was then immersed and fixed in 10% neutral formaldehyde for 12 hours and then in ML-NRS three times in volume for 6 to 12 hours. The lymph nodes stood out as deep blue nodules on the background of yellow fat. All identified lymph nodes were resected and analyzed histologically. CK20 - IHC was then applied to positive lymph nodes in routine pathological examination.ResultsThe conventional preparation of lymph nodes yielded a total of 1456 lymph nodes in the 46 specimens and 130 of them were positive for metastasis in routine HE staining. The remaining negative ones were examined by CK20 immuno-histochemical staining and 63 additional nodes were detected. An further application of MLNRS identified 1377 additional lymph nodes in total, and 106 were positive in routine HE staining. The remaining negative ones were examined by CK20 immunohistochemical staining and 102 additional nodes were detected.There was significant difference between these two methods in the detection rate of positive lymph nodes. The specimens were aligned to different group according to detection method and staged with N and PTNM classification according to identified positive lymph nodes. And there was significant difference in stage changes among groups after statistical analysis.