Expansion of indications for endoscopic treatment of undifferentiated mucosal gastric cancer: analysis of intramucosal spread in resected specimens.

PURPOSE: The aim of this study was to pathologically investigate the developmental pattern of undifferentiated mucosal gastric cancer and to determine safe surgical margins for curative resection by endoscopic resection.
RESULTS: Intramucosal cancer spread, or the width of the proliferative zone, was pathologically investigated in 47 cases of undifferentiated mucosal gastric cancer of size 20 mm or smaller without ulceration (scars). The 47 cases comprised 40 IIc and 7 IIb cases. The IIc cases consisted of 5 (12.5%) of intermediate-layer type (cancer localized at the intermediate layer of the mucosa), 31 (77.5%) of superficial type, and 4 of whole-layer type (10%). The IIb cases consisted of six of intermediate-layer type (85.7%) and one of superficial type (14.3%). The width of the proliferative zone in the 40 IIc cases ranged from 0 to 2,390 microm (average 605.5 microm). There was no significant correlation between width of proliferative zone and background mucosa. With regard to lesion size, average width was 243.6 microm in cases with longest diameter <or=5 mm, while it was significantly larger (617.1 microm) in cases with diameter >5 mm.
CONCLUSIONS: In endoscopic treatment of undifferentiated mucosal gastric cancer of size 20 mm or smaller without ulceration (scars), the lateral safety margin should be 3 mm or more.