Biological behavior of the intramucosal Helicobacter pylori-negative undifferentiated-type early gastric cancer: comparison with Helicobacter pylori-positive early gastric cancer.

The differences in the growth morphology, proliferative ability, and background mucosa of the cancer between Helicobacter pylori (HP)-positive (HP+) gastric cancer (GC) and HP-negative (HP-) GC are still unclear. To clarify the differences, we compared the characteristics of the two types of cancer. Of the 91 patients with undifferentiated-type early GC who underwent endoscopic treatment at our hospital between August 2005 and April 2011, 23 HP- GC patients (all of whom had signet ring cell carcinoma measuring 20 mm or less in diameter) and 46 HP+ GC patients with signet ring cell carcinoma measuring 20 mm or less in diameter (out of a total of 68 HP+ GC patients) were enrolled in this study. Endoscopic atrophy and background mucosa were classified according to the updated Sydney system. The proliferative capacity of the cancer was assessed by examining the MIB-1 labeling index. With regard to the growth in the mucosal layer, the proportion of patients with cancer confined to the proliferative zone was significantly higher in the HP- GC group. Moderate or severer atrophy, intestinal metaplasia, mononuclear cell infiltration, and neutrophil infiltration according to the updated Sydney system were significantly commoner in the HP+ GC patients. Also, the MIB-1 labeling index was significantly higher in the HP+ GC group. HP+ GC appeared to show a higher proliferative capacity, more extensive spread, and more rapid progression, and inflammation associated with HP infection was suggested to be involved in the proliferation of this type of GC.