Incomplete Intestinal Metaplasia in Pyloric Gland Mucosa of Helicobacter pylori-Naïve Stomachs: A Prospective Multicenter Histopathologic Study.

Helicobacter pylori (Hp)-naïve gastric mucosa has been characterized histologically by the absence of Hp organisms, atrophy, and intestinal metaplasia (IM). We conducted a prospective multicenter study to clarify the prevalence and clinicopathologic features of IM in the Hp-naïve stomach. Hp-naïve individuals with regional gastric mucosal abnormalities detected by endoscopy were enrolled. Biopsies were obtained from target lesions and adjacent mucosa. IM frequency and Updated Sydney System (USS) scores were assessed by glandular background (pyloric vs. fundic) in both target and adjacent samples. Among 52 target and 56 adjacent samples, pyloric and fundic gland mucosa accounted for 28 and 24 target samples and 21 and 35 adjacent samples, respectively. IM was detected exclusively in pyloric gland mucosa of target lesions (46.4% vs. 0%, p < 0.05) and was absent in adjacent mucosa. Atrophy scores were low overall but significantly higher in pyloric than fundic gland mucosa in both target lesions (median [IQR], 1 [1-2] vs. 0 [0-1], p < 0.05) and adjacent mucosa (1 [1-2] vs. 1 [0-1], p < 0.05). All IM lesions were classified as incomplete type, showing predominant small intestinal-type differentiation with residual gastric foveolar markers. Histological evaluation of Hp-naïve gastric mucosa should be region-specific, with attention to glandular architecture.