MIXED INTESTINAL‐ AND DIFFUSE‐TYPE HISTOLOGY IS A RISK FACTOR FOR LYMPH NODE METASTASIS OF SUBMUCOSAL INVASIVE GASTRIC CANCER

Background: Endoscopic submucosal dissection is expected to increase the number of node‐negative submucosal invasive gastric cancers, particularly differentiated‐type adenocarcinomas that can be treated conservatively. Methods: Two hundred and seven consecutive surgically treated cases of differentiated‐type early gastric cancer with submucosal invasion were analyzed clinicopathologically. Comparison was made between patients with node‐positive (n = 33) and node‐negative cancer (n = 174). Whole sections of surgical specimens were reviewed and reclassified as pure intestinal type or mixed type. The intramucosal and submucosal components were also described histologically, and the depth of invasion from the muscularis mucosae as well as the width of submucosal invasion was measured. Results: Twenty‐four of 33 (73%) node‐positive cases were of the mixed type, whereas 71 of 174 (41%) node‐negative cases were of the mixed type (P < 0.01). As for the intramucosal histology, the ratio of mixed‐type was also higher in the node‐positive group (58% vs 34%; P < 0.05). Other factors associated with lymph node metastasis were larger tumor size (P = 0.003), deeper submucosal invasion (P < 0.001) and wider submucosal extension (P = 0.004), and lymphatic permeation (P < 0.001). Multivariate analysis demonstrated that lymphatic permeation (P = 0.001, OR 4.76), and mixed‐type histology (OR 2.56) were independent risk factors. Conclusions: Histological heterogeneity is a risk factor for metastasis of submucosal invasive gastric cancer to lymph nodes. Heterogeneity of mucosal components is also a significant risk factor and thus a good predictor of lymph node metastasis, potentially useful in distinguishing patients ineligible for conservative therapy.