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

## TL;DR

A rare gastric glomus tumor was misdiagnosed as a neuroendocrine tumor, highlighting the importance of specific immunostaining for accurate diagnosis.

## Contribution

This case emphasizes the diagnostic value of smooth muscle actin staining in distinguishing glomus tumors from neuroendocrine tumors.

## Key findings

- Histology showed small round cells in nests and trabeculae with vessel-rich stroma and focal calcification.
- Immunohistochemistry was negative for CD117, HMB45, and chromogranin A but positive for smooth muscle actin.
- The diagnosis of gastric glomus tumor was confirmed, emphasizing the need for specific markers in limited biopsy samples.

## Abstract

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.