Impact of immunohistochemically identified lymphatic invasion on nodal metastasis in early gastric cancer

Background. Among various clinical and pathological findings, lymphatic invasion (Ly) is the strongest risk factor for nodal metastasis in gastric cancer. However, the diagnosis of Ly is subjective and often inaccurate because of the difficulty of detecting lymphatic vessels with conventional hematoxylin and eosin (HE) staining. Methods. The distribution of lymphatics in the normal gastric wall was immunohistochemically characterized using a new selective marker of lymphatic endothelium, D2-40, in surgical specimens resected for early gastric cancer (EGC). Then, Ly in the primary lesion was reevaluated, and the positive (PPV) and negative (NPV) predictive values for nodal metastasis were comparatively examined for Ly detected by HE staining (Ly-HE) and by immunohistochemical staining (Ly-IM) in 131 cases of EGC. Results. D2-40-positive lymphatic vessels were observed in the deep proper mucosal layer, and the lymphatic vessel density (LVD) was extremely high in the muscularis mucosa (MM) layer. The number of Ly-IM-positive cases (15/131) was higher than the Ly-HE-positive cases (10/131). In 48 cases of intestinal-type cancer, Ly-IM had a PPV of 33.3% (2/6) and anNPV of 100% (42/42), which was more accurate than the corresponding figures for Ly-HE (25% and 98%, respectively). In contrast, the accuracy of Ly-IM was similar to that of Ly-HE in 83 cases of diffuse-type cancer. Conclusion. Lymphatic vessels are most densely distributed in the MM layer in the gastric wall. Immunohistochemical identification of lymphatics is useful to increase the accuracy of diagnosing Ly in resected gastric EGCs. Ly-IM is superior to Ly-HE as a predictor of nodal metastasis, at least for intestinal-type EGC. © 2006 International and Japanese Gastric Cancer Association.