許旺氏細胞瘤（schwannoma）通常是生長緩慢，症狀不明顯的間質細胞腫瘤，腫瘤由鞘膜包覆，源自於周邊神經叢的許旺氏細胞（Schwann cell）。此類腫瘤好發於聽神經，即所謂聽神經瘤（acoustic neuroma），在胃部發生較為罕見。胃部的許旺氏細胞瘤生長自胃壁的神經叢，佔所有胃部腫瘤的百分之零點二。然而，在胃腸道的間質細胞瘤當中，腸胃道基質瘤（gastrointestinal stromal tumors, GISTs）最為常見，其中胃部的腸胃道基質瘤佔了六至七成。在內視鏡檢查下，胃部的許旺氏細胞瘤（gastric schwannoma）與腸胃道基質瘤皆以黏膜下腫瘤表現，兩者極為相似。胃部的許旺氏細胞瘤常見的症狀表現以出血為主，腹部的疼痛與不適感次之。在此案例報告中，我們提出一位七十七歲婦女，因為逐漸虛弱無力於神經科求診，實驗室檢查發現貧血後，於胃腸內科安排胃鏡而發現胃體部黏膜下腫瘤，腫瘤中央出現潰瘍與出血後徵象。經腹部電腦斷層檢查後，初步臆診為腸胃道基質瘤並進行部分胃切除術。然而，術後病理報告顯示該腫瘤為胃部許旺氏細胞瘤。此案例提醒臨床醫師在內視鏡、影像學檢查發現黏膜下、向外生長的胃部腫瘤時，應考慮許旺氏細胞瘤之可能。同時，此案例也強調單純的貧血、未合併明確腹部症狀，儘管無明確胃腸道出血證據時，盡早進行內視鏡檢查的價值。最後，六個月後本案例的內視鏡與實驗室檢查，可發現病人胃部無腫瘤復發跡象，血色素回復正常範圍。

Gastric schwannomas (GSs) are generally slow-growing, asymptomatic encapsulated tumors of mesenchymal origin arising from Schwann cells of nerve plexus within the gastric wall. Schwannomas are rare in the stomach, and account only 0.2% of all gastric tumors. Among mesenchymal tumors in the gastrointestinal (GI) tract, gastrointestinal stromal tumors (GISTs) are the most common, and 60–70% of them occur in the stomach. Under endoscopic examination, GS/GSs and GIST/GISTs appear grossly similar as firm submucosal neoplasm. The most common presenting symptom is upper gastrointestinal bleeding, followed by abdominal pain. Here, we report a 77-year-old lady presented with progressive weakness, and received prompt esophagogastroduodenoscopy (EGD) due to anemia. The EGD revealed a submucosal tumor with hemorrhagic ulceration at the middle to lower body of the stomach. After contrast-enhanced computed tomography (CT), the patient received partial gastrectomy with initial impression of GIST/GISTs, but confirmed as schwannoma postoperatively. This case highlights the importance of considering schwannomas as a differential diagnosis when preoperative imaging studies revealed a submucosal, exophytic gastric mass. The case also underscores the value of prompt EGD survey even for normocytic anemia with negative stool occult blood and nonspecific GI symptoms, especially when it comes to the elderly. (