Lymph node revealing solution in gastric carcinoma does not provide upstaging of the N-status

Staging of gastric carcinoma depends on exact lymph node status. However, very small lymph nodes can easily be missed during routine examination as they are obscured by the surrounding adipose tissue. The purpose of the present study was to verify the usefulness of a lymph node revealing solution (LNRS) in gastric cancer and compare its accuracy concerning the detection of lymph node metastases to immunostaining with cytokeratin antibodies. A total of 11 consecutive patients underwent standardized D2 gastrectomy for primary gastric adenocarcinoma. Non-fixed, the entire surgical specimen was searched for lymph nodes by palpation and visualization. The remaining tissue was immersed for 24 h in LNRS. The lymph nodes stood out as white chalky nodules on the background of yellow fat. All identified lymph nodes were resected and analyzed histologically. In 5 patients with pN0 status, immunostaining of the lymph nodes was performed using cytokeratin-specific antibodies. The conventional preparation of lymph nodes from the unfixed tissue yielded a total of 452 lymph nodes (mean 41.1 lymph nodes/patient; range, 26 to 56), and 201 of them had a pN0 status. After fixation using LNRS, 138 additional nodes could be detected (mean 12.5 lymph nodes/patient; range, 3 to 21), and 70 of them with a pN0 status. The detection rate of extremely small lymph nodes (<3 mm) increased by 27% compared to the conventional preparation technique (p=0.0017). After application of the LNRS lymph node analysis, it was not necessary to change the UICC node (N) stage in any cases. Additionally, we performed immunostaining in 5 specimens with pN0 status. In one patient, 10 micrometastases/disseminated tumour cells were detected. Thus, after immunohistochemical re-evaluation, one patient had to be upstaged pN(i+). By performing standardized LAD systematically and detailed lymph node preparation by the pathologist, a routine application of the LNRS method in gastric carcinoma is not recommended. Immunohistochemical techniques aid in identifying micrometastatic disease in lymph nodes missed in routine H&E staining in order to define the pN(i) status according to the TNM classification.