PTH-192 Gastric adenocarcinoma of diffuse type develops on a healthy-looking mucosal background, unlike intestinal type gastric adenocarcinoma

Abstract

Introduction Intestinal type gastric adenocarcinoma develops in an inflammatory and atrophic background with profound loss of secretory cells. Little is known about background gastric mucosa in diffuse type adenocarcinoma. Method Total gastrectomy specimens from non-tumoural body mucosa were selected from 22 patients with diffuse type gastric adenocarcinoma. A frequency-matched group of 22 specimens from patients with intestinal type gastric adenocarcinoma were included as comparison. Well-oriented sections were immunostained for H/K ATPase (parietal cells) and Pepsinogen I (chief cells). Absolute mucosal cell density (per mm 2 ) was measured and expressed as mean (±SD). Inflammatory changes were scored by a semi-quantitative method in both groups. Results The background densities of parietal cells (PC) and chief cells (CC) were significantly higher in diffuse type than intestinal type cancers, being 665 (±216) vs. 412 (±170) cells/mm 2 , p .001; and 847 (±259) vs. 443 (±206) cells/mm 2 , p .001, respectively. Glandular layer was significantly thicker in diffuse type [811 (±161) µm] vs. intestinal type [610 (±140) µm, P .001]. In contrast, length proportion of intestinal metaplasia was higher in intestinal type than diffuse type [23% (±30) vs 4% (±13), p .005]. Mucosal inflammation was less in diffuse versus intestinal type adenocarcinoma expressed by infiltration score of mononuclear cells ( p = 0 .011) and reactive changes ( p = 0 .005), but not in polymorphonuclear cell. Secretory cell densities and inflammation were inversely correlated in both cancer types. Conclusion The background mucosa in diffuse type gastric adenocarcinoma is much healthier than that of intestinal type adenocarcinoma, with more functional secretory cells, thicker gastric glands, less atrophy, less inflammation and less intestinal metaplasia. This suggests the existence of separate aetiological pathways leading to these distinct types of gastric adenocarcinoma. Disclosure of interest None Declared.