Background: Extranodal metastasis is an isolated tumor nodule without a residual lymph node structure and has been reported as a poor prognostic factor in gastric cancer. The aim of this study is to assess the prognostic value of extranodal metastasis, especially from the viewpoint of its anatomical distribution.
Methods: A total of 139 consecutive gastric cancer patients who underwent curative surgery with lymph node metastasis between 2008 and 2009 were included. Clinicopathological features and patient survival outcomes were retrospectively assessed. Patients with extranodal metastasis were subdivided into two groups: perigastric extranodal metastasis, located near the perigastric area (#1-#7 according to the Japanese classification of gastric carcinoma 15th edition), and extra-perigastric extranodal metastasis, located alongside the major vessels (#8-#12).
Results: Extranodal metastasis was found in 51 patients (37%), and it was more frequent in those with bulky, ≥pT3, and pStage III tumors. All patients with extra-perigastric extranodal metastasis had recurrence, resulting in a 0% 5-year overall survival rate, which was significantly worse than that of patients with perigastric extranodal metastasis (59%), or those without extranodal metastasis (84%; P < 0.001). Multivariable analysis identified the presence of extra-perigastric extranodal metastasis as an independent poor prognostic factor.
Conclusions: Extranodal metastasis, especially extra-perigastric extranodal metastasis, was a pivotal poor prognostic factor in node-positive gastric cancer. Recognizing extra-perigastric extranodal metastasis would help provide optimal therapeutic options to these high-risk patients.