A Rare Case of Splenunculus Buried within the Stomach.

Background: Accessory spleen, or splenunculus, is a congenital anomaly resulting from failure of splenic anlage fusion during embryonic development. It is most commonly located near the splenic hilum or pancreatic tail and rarely occurs within the stomach wall. Gastric accessory spleen is a rare entity that may mimic submucosal neoplasms such as gastrointestinal stromal tumour, posing a diagnostic challenge. Case presentation: We report the case of a 37-year-old male presenting with a 3-month history of epigastric pain, dyspepsia, and nausea. Endoscopy revealed a 2.5-3 cm submucosal mass in the gastric fundus with intact mucosa, and erosive antral gastritis. Endoscopic ultrasound demonstrated a 22.6 × 17.2 × 23.3 mm hypoechoic, homogeneous lesion arising from the third layer of the gastric wall. Endoscopic ultrasound-guided fine needle biopsy (EUS-FNB) showed lymphoid aggregates with characteristic vascular structures lined by CD8-positive littoral cells and CD68/PGM1-positive macrophages. Immunohistochemistry excluded epithelial, neuroendocrine, and lymphoproliferative neoplasms, confirming the diagnosis of gastric accessory spleen. Discussion: This case is distinctive because the patient had no prior splenectomy or trauma and was diagnosed preoperatively using EUS-guided biopsy-avoiding unnecessary surgery. Gastric accessory spleen remains a rare but important differential diagnosis for submucosal gastric lesions. Recognition of its imaging and histopathologic features can prevent misdiagnosis and overtreatment. Conclusion: Gastric accessory spleen is a benign, rare condition that should be considered in patients presenting with gastric submucosal masses. Non-invasive diagnostic modalities such as EUS-FNB and immunohistochemistry are essential to achieve an accurate diagnosis and to avoid unnecessary surgical resection. LEARNING POINTS: Gastric accessory spleen is a rare, usually incidental finding with no clinical significance.It should be considered as one of the differential diagnoses of gastric subepithelial lesions.Despite the fact that histopathologic evaluation remains the gold standard, both nuclear scintigraphy and enhanced computed tomography scan may be useful in the diagnosis of ectopic splenic tissue.