S6315 Gastric Gastrointestinal Stromal Tumor Masquerading as Iron Deficiency Anemia and Abdominal Pain: A Rare but Critical Diagnosis

Introduction: Gastric tumors can encompass a variety of pathologies including adenocarcinoma, leiomyoma, and lipoma. Gastrointestinal stromal tumors (GISTs), while relatively rare, account for approximately 0.1% to 3% of all gastrointestinal (GI) malignancies. When present, GISTs most commonly originate in the stomach, though up to 20% can be found in the small intestine. These tumors are typically present later in life, with a median age of diagnosis around 60 years. Clinical presentations may vary, ranging from nonspecific abdominal pain, distention, palpable masses, GI bleeding or symptoms of chronic anemia. We present a case of a GIST diagnosed in a patient who initially presented with abdominal pain and iron deficiency anemia. Case Description/Methods: A 71-year-old man with a medical history of colon cancer status post hemicolectomy, hypertension, and osteoarthritis presented with complaints of persistent abdominal pain. Initial laboratory workup revealed a hemoglobin (Hgb) of 7.5 g/dL, mean corpuscular volume (MCV) 61.2 fL, ferritin of 10 ng/mL, and iron saturation of 4%, consistent with iron deficiency anemia. Computed tomography (CT) imaging of the abdomen and pelvis with contrast identified a 2.4 × 2.2 × 1.9 cm heterogenous gastric mass along with enlarged left retroperitoneal lymph nodes. Subsequent esophagogastroduodenoscopy (EGD) with endoscopic ultrasound (EUS) visualized a heterogenous, malignant-appearing mass originating from the muscularis propria with hyperechoic features. Immunohistochemical staining was positive for CD117 and DOG1, confirming the diagnosis of gastrointestinal stromal tumor. Discussion: Although GISTs are often benign, approximately 30% demonstrate malignant behavior. In rare instances, they may also occur outside the gastrointestinal tract, including the omentum and retroperitoneum. Management strategies are based on tumor characteristics such as primary site, tumor size, and mitotic count. Treatment options include surgical resection for localized tumors, while unresectable and metastatic GISTs are managed with tyrosine kinase inhibitors. This case highlights the importance of considering gastrointestinal stromal tumors in the differential diagnosis of unexplained iron deficiency and abdominal pain, particularly in older adults.