Incidence of lymph node metastasis in intramucosal gastric cancer measuring 30 mm or less, with ulceration; mixed, predominantly differentiated-type histology; and no lymphovascular invasion: a multicenter retrospective study.

Background: Intramucosal gastric cancer, ≤3 cm (≤30 mm) with ulceration, and mixed histology (predominantly differentiated), was previously considered curative after endoscopic resection, and additional surgery was thought to be unnecessary. However, as the evidence base for these criteria remains insufficient, the Japanese Gastric Cancer Treatment Guidelines, ver. 3 (2010) specify that this pathology should be considered noncurative and recommend additional surgery. We report the frequency of lymph node metastasis in patients with these conditions based on a multicenter study.

Methods: Of patients with early gastric cancer who underwent gastrectomy with lymph node dissection, those with a mixed, predominantly differentiated tumor type, ulceration, a tumor diameter ≤3 cm, and no lymphovascular invasion were entered into this study.

Results: Four hundred and seven patients met the criteria, 21 of whom were excluded owing to a lack of available information. Thus, a total of 386 patients were included in the analysis, from 37 of the 42 member institutions. The mean study duration was 125 months. The most common combination of mixed histology was tub2 + por (67 %). None of the 386 patients had lymph node metastasis (95 % confidence interval, 0-0.8 %).

Conclusion: The results of this retrospective study indicate that the risk of lymph node metastasis was less than 1 % among patients with the criteria defined here, considered to be criteria for noncurative resection as per the current guidelines, and suggest that observation alone without additional surgery may result in a good outcome.