Endoscopic ultrasound features differentiating nonumbilicated gastric heterotopic pancreas from GISTs: a pilot study

Abstract Background and Aims Nonumbilicated gastric heterotopic pancreas (HP) is frequently mistaken for gastrointestinal stromal tumors (GISTs), leading to unnecessary resection. We aimed to identify EUS features that distinguish nonumbilicated HP from GISTs. Methods This retrospective single-center pilot study included 115 patients who underwent EUS followed by resection. Pathology confirmed nonumbilicated HP in 14 patients and GISTs in 101. Two independent reviewers, blinded to pathology, assessed seven EUS features. We combined the three most specific features and calculated diagnostic performance with 95% confidence intervals. Results Conventional EUS alone correctly identified nonumbilicated HP in only 4 of 14 patients (28.6%). Among the individual EUS features, third‑layer origin, mixed echogenicity, and soft‑to‑medium elasticity (Giovannini scores 1–3) had specificities of 100% (95% confidence interval (CI) 96.3–100.0%), 86.1% (95% CI 77.8–92.2%), and 84.4% (95% CI 75.5–90.9%), respectively. When combined, these three features achieved 100% specificity and 100% positive predictive value. Among the 107 patients with complete elastography data, the sensitivity was 63.6% (95% CI 30.8–89.1%), and the accuracy was 96.3% (95% CI 90.8–98.9%). No GIST met any of the three criteria. Conclusions In this pilot cohort, the combination of third-layer origin, mixed echogenicity, and soft-to-medium elasticity identified nonumbilicated HP with high specificity against GISTs. These findings remain hypothesis-generating and await validation in larger prospective cohorts.