Gastric Glomus Tumor with Neuroendocrine Features: A Diagnostic Pitfall for Neuroendocrine Tumors

A 60-year-old woman with hypertension and hyperlipidemia was referred for an incidentally detected gastric subepithelial mass during screening endoscopy. Esophagogastroduodenoscopy revealed a 10 mm dimple in the antrum, and contrast-enhanced CT showed a 2.5 cm enhancing oval lesion. Laparoscopic partial gastrectomy with intraoperative endoscopic guidance was performed. Gross examination revealed a 3.0 × 2.0 × 1.0 cm pale, firm nodule. Histology showed small round cells arranged in nests and trabeculae within the muscularis propria, with numerous vessels and focal calcification. Immunohistochemistry was negative for CD117, HMB45, and chromogranin A, but demonstrated strong smooth muscle actin positivity, weak synaptophysin reactivity, and focal CD56 staining. The findings confirmed a gastric glomus tumor with neuroendocrine features. Smooth muscle actin immunostaining is essential to distinguish gastric glomus tumors from neuroendocrine tumors when biopsy material is limited, ensuring accurate diagnosis and appropriate management.