Analysis of sentinel node involvement in gastric cancer

Background & Aims: Sentinel node navigation surgery (SNNS) is performed for patients with early gastric cancer. Because sentinel nodes (SNs) to gastric cancer exist but they have not been well-described, we attempted to validate the SN concept at the micrometastasis level. Methods: For 53 patients who underwent curative gastrectomy for T1/T2 (< 4 cm) N0 gastric cancer, SNNS was performed with radioactive tin colloid and/or indocyanine green, and subsequent modified D1 lymphadenectomies were added. Whole formalin-fixed paraffin-embedded tissues of all resected lymph nodes from these patients were cut into 5-mu m thick serial step sections at 85-mu m intervals, and occult metastases were examined immunohistochemically. Results: metastases were detected in 3 (1.5%) of 204 SNs and 3 (0.33%) of 901 non-SNs in pN0 cases and in 18 (46%) of 39 SNs and 3 (1.9%) of 158 non-SNs in pN1 cases. On a patient basis, metastases were detected in 4 (9%) of 46 pN0 patients, 2 (4%) each in SNs and non-SNs, and in 7 pN1 patients, of whom 7 and 4 had SN and non-SN metastases, respectively. The sensitivity, false-negative rate, and accuracy of SN identification by SNNS were 82%, 18%, and 96%, respectively, at the occult metastasis level. However, on the basis of the concept of the sentinel lymphatic station (SLS), which represents all lymphatic stations to which SNs belong, metastases were always limited to the lymph nodes in SLS in the 11 cases with metastases. Non-SN metastases occurred in 3 (60%) of 5 patients with SN metastases > 2.0 mm in diameter but not in 4 patients with SN metastases <= 2.0 mm in diameter. Conclusions: The sentinel node concept held true at the occult metastasis level in 96% of patients with gastric cancer, and the accuracy of SNNS was elevated to 100% by introducing the concept of the sentinel lymphatic station. The size of SN metastasis was a predictive factor for metastasis beyond the sentinel node.