Laparoscopic lymphatic mapping and sentinel node biopsies for early-stage gastric cancer: the cause of false negativity.

Sentinel node (SN) biopsies might be useful for performing minimally invasive surgery without interrupting surgical curability. This study examined the cause of false negativity during laparoscopic lymphatic mapping and SN biopsies for early-stage gastric cancer. Thirty-seven patients with gastric cancer (preoperative stage T1-2 or N0) who underwent laparoscopic lymph node mapping and SN biopsies between March 2001 and June 2004 were enrolled in this study. The tracer, patent blue and technecium-99m-labeled tin colloid, was injected endoscopically. Blue-stained or radioactive nodes were defined as SNs. Gastrectomy with lymphadenectomy was performed then the results of the SN biopsies were compared with the final diagnosis of the removed lymph nodes in permanent sections. Sentinel nodes were successfully identified in 35 patients (94.6%), and they were positive in 3 of 4 patients with metastatic lymph nodes; sensitivity was 75% and specificity was 100%. Sentinel node status could therefore be used to diagnose lymph node status with 97.1% accuracy. Of 6 SNs with metastasis, 5 showed radioactivity, and only 2 were blue stained. In the false negative case, a radioactive SN with metastasis in the right paracardial region was missed during laparoscopic mapping. An error in laparoscopic intracorporeal detection of the radioactive node with metastasis occurred because we could not eliminate the shine-through effect. We found that during laparoscopic SN mapping there is a high risk of false negativity with SNs located in the right paracardial region. To apply laparoscopic SN mapping to early-stage gastric cancer patients, the shine-through effect must be eliminated because radiotracers are essential for this method.