Undifferentiated-type component mixed with differentiated-type early gastric cancer is a significant risk factor for endoscopic non-curative resection.

BACKGROUND AND AIM: Previous studies of surgical specimens have found that the presence of mixed histological components in differentiated-type early gastric cancer (EGC) is a risk factor for lymph node metastasis and indicates greater malignancy. As there have been no reports on its endoscopic treatment, we examined endoscopic curative resection in relation to differentiated-type-predominant mixed-type (MT).

METHODS: This was a single-center, retrospective study. Subjects were 2585 differentiated-type EGC in 2551 patients treated with endoscopic submucosal dissection (ESD) in our hospital between March 2005 and January 2016. These lesions comprised 2231 cases of curative resection and 354 cases of non-curative resection. Histologically, 2339 lesions were pure differentiated-type (PDT) and 246 lesions were MT. Rates of curative resection were compared, according to tumor size, between different histological types.

RESULTS: When curative and non-curative cases were compared using multivariate analysis among lesions measuring ≤20 mm for factors other than those determining curative resection, significant differences were obtained for tumor diameter, ulcer, and MT. Among lesions measuring 21-30 mm, ulcer and MT were associated with significant differences. Among lesions measuring >30 mm, upper region and MT were associated with significant differences. Curative resection rates, in relation to histological type among lesions measuring ≤20 mm, were 93.4% for PDT and 63.4% for MT, whereas corresponding rates were 85.1% and 60.0%, respectively, among lesions measuring 21-30 mm, and 55.3% and 30.2%, respectively, among lesions measuring >30 mm.

CONCLUSION: We found that MT was a risk factor for non-curative resection irrespective of lesion size.