Autoimmune gastritis (AIG) predisposes to type I gastric neuroendocrine tumors (NETs), which are usually well-differentiated and of low malignant potential. Early endoscopic recognition is critical for adequate management and follow-up. This study aimed to assess the prevalence of gastric NETs among patients with AIG and explore potential endoscopic and clinical correlations.

A retrospective study was conducted including patients with histologically confirmed AIG diagnosed between 2010 and 2025 at a tertiary referral center in Northern Greece. Demographic, clinical, and endoscopic data were reviewed. Archived endoscopic images were re-evaluated and graded according to the Kimura–Takemoto classification to determine the extent of atrophy. The prevalence, localization, histological grade, and management of NETs were analyzed. The chi-square (χ²) test was used to examine associations between atrophy severity and NET occurrence.

A total of 210 patients were included (median age 61.8 years, range 34–84; 60.9% female). Endoscopic atrophy distribution was: C-1, 18%; C-2, 15.2%; C-3, 31.4%; O-1, 8%; O-2, 8.5%; and O-3, 18.5%. Type I gastric NETs were diagnosed in 47 patients (22.3%), with a median size of 0.5 cm (range 0.2–3 cm) and median age 56.6 years (range 34–75); 46.8% were male. Most lesions were located in the corpus (85%), and were graded as G1 in 70% and G2 in 30%. Endoscopic resection was performed in 51%, and surgical resection in 4.2% for lesions >1 cm. Severe atrophy (C-3/O-3) was significantly associated with NET occurrence (p = 0.007). No other significant associations were observed.

Type I gastric NETs were identified in 22.3% of patients with autoimmune gastritis, predominantly as small, well-differentiated lesions. The severity of endoscopic atrophy correlated significantly with tumor development. These results support structured endoscopic surveillance and grading of atrophy in AIG as essential for early detection and timely management of type I gastric NETs.