Background: The clinical application of sentinel node navigation surgery (SNNS) for patients with gastric cancer requires accurate intraoperative diagnosis of lymph node metastasis. However, the clinical significance of the diagnosis of lymph node micrometastasis for gastric cancer has not been established. In this study, we evaluated lymph nodes dissected during SNNS by immunohistochemistry with anti-cytokeratin antibody (IHC) staining for gastric cancer to investigate the usefulness of SNNS.
Patients and methods: The subjects were 130 patients with gastric cancer (3,381 lymph nodes) who underwent SNNS with infrared ray observation and lymph node dissection of D1+α or more. The dissected lymph nodes were stained with IHC (CAM 5.2), and the results were compared with intra- and postoperative diagnoses by hematoxylin and eosin (H&E) staining. In addition, the association of metastatic lymph nodes and ICG-positive lymph nodes was examined.
Results: The number of patients (lymph nodes) with lymph node metastasis by HE and IHC staining was 16 (52 nodes) and 31 (91 nodes), respectively. Fifteen patients (27 nodes) diagnosed with pN0 by HE staining were diagnosed to be metastatic by IHC staining. The tumor depth of these patients was pT1 in ten patients (m, 3; sm, 7) and pT2 in five (mp, 4; ss, 1). Regarding the histological type, three patients were classified as well-differentiated type, while six patients each had moderately and poorly differentiated types. The grade of lymphatic invasion was ly0 in 5, ly1 in 6, and ly2 in 4, respectively. Histological assessment of 27 IHC-positive and HE-negative cells indicated 5 single cells, 16 clusters, and 6 micrometastases. These lymph nodes were all included in the sentinel nodes (SN) identified during surgery. All but one patient (0.8%) were recurrence-free at 2-8 years after surgery (median 74.7 months). The one patient developed anastomotic recurrence 4.5 years after the first operation and died.
Conclusion: Since all 27 lymph nodes in 15 patients with metastasis by IHC staining but not by HE staining were micrometastasis or less and included in the SN, ICG-positive lymphatic basin dissection by SNNS with infrared ray observation seems to be an adequate method of lymph node dissection for gastric cancer.