Rare Subepithelial Mass Diagnosed as Gastric Splenosis via EUS-FNA

A 20-year-old woman was referred for evaluation of a gastric subepithelial mass, noted incidentally on an esophagogastroduodenoscopy performed for evaluation of dyspepsia (Figure 1). She had a past medical history of Diamond-Blackfan syndrome status post bone marrow transplant, and recurrent acute pancreatitis status post total pancreatectomy with splenectomy 4 years before presentation. Endoscopic ultrasound (EUS) revealed the presence of a 21 x 18-mm round, hypoechoic, and homogenous mass in the cardia, with an echogenicity reminiscent of splenic tissue (Figure 2). No other foci of ectopic splenic tissue were found on cross-sectional imaging. Endosonographic borders were well defined, and the lesion appeared to be localized within the muscularis propria without extragastric extension. Cytology smears and hematoxylin and eosin stains fine-needle aspiration biopsies showed a population of polymorphous small lymphocytes, interspersed granulocytes, and frequent hemosiderin laden macrophages (Figure 3). This population was intimately associated with small vessels, highlighted by CD34 and CD8 immunohistochemical stains (Figure 4). Coexpression of CD34 and CD8 is consistent with splenic sinusoids.