Gastrointestinal Stromal Tumor (GIST) Arising in the Setting of a Large Hiatal Hernia: A Case Report

Background: The occurrence of a gastric neoplasm within a hiatal hernia is a rare clinical entity that poses significant diagnostic challenges. While imaging may initially suggest more common malignancies like adenocarcinoma, gastrointestinal stromal tumors (GISTs) should be considered as a critical differential diagnosis due to their distinct management implications. Case Presentation: A 53-year-old Somali male presented with fatigue, dizziness, early satiety, and shortness of breath on exertion. CT revealed a large hiatal hernia with an 8.4× 6.5 cm heterogeneous mass arising from both the herniated and non‑herniated portions of the gastric wall, and extending into the esophageal lumen. Endoscopic biopsies were non-diagnostic. Surgical resection confirmed a high-risk GIST (pT4, 8.4 cm, mitotic index 8/50 HPF). The patient received adjuvant imatinib 400 mg daily. Follow-up CT on August 10, 2025, showed a 6.2× 6.0 cm recurrent lesion. Conclusion: A hiatal hernia with mass should prompt a strong suspicion for malignancy. Although gastric adenocarcinoma is more commonly suspected, GIST should remain an important differential. This case highlights the essential role of immunohistochemistry in achieving a definitive diagnosis and underscores the aggressive nature of high-risk GISTs. This necessitates complete surgical resection, consideration of adjuvant therapy, and rigorous radiological surveillance.