Nature of white opaque substance in gastric epithelial neoplasia as visualized by magnifying endoscopy with narrow-band imaging

Background and Aims: Magnifying endoscopy (ME) with narrow-band imaging (NBI) revealed a white opaque substance (WOS) within the superficial part of the gastric neoplasia; however, its nature has remained obscure. A WOS noted within the duodenum was reported to comprise lipid droplets (LD) absorbed by the duodenal epithelium. We attempted to ascertain whether the WOS within gastric neoplasia could also comprise LD and whether the presence of this WOS could be correlated with a specific phenotype. Methods: Forty-three patients with early gastric epithelial neoplasia underwent ME with NBI. The presence or absence of WOS in the neoplasias was recorded based on the findings of ME with NBI. One biopsy specimen was taken from each of the neoplasias. Cryostat sections underwent oil red O staining for LD. Serial sections were immunostained using the first antibody of CD10, MUC2, CDX2, human gastric mucin, MUC5AC and MUC6. The tissue phenotype was classified as intestinal (I), gastric (G) and gastrointestinal (GI) type based on the results of immunostaining. In total, 49 gastric neoplasias from 43 patients were investigated. Results: Prevalence of LD in WOS-positive versus WOS-negative lesions was 96.2% (25/26) and 4.3% (1/23), respectively (P < 0.001, Fisher's exact test). WOS was present in GI- and I-type lesions, but not in G-type lesions. Conclusions: WOS may be LD that have been accumulated in the superficial part of the gastric neoplasia of a certain intestinal phenotype.