S2932 Ectopic Spleen Tissue Mimicking Gastrointestinal Stromal Tumor, a Case Report of a Gastric Subepithelial Lesion

Abstract

INTRODUCTION: Gastric subepithelial lesions (SEL) are found as often as 1 in 300 endoscopies. Indolent growing gastric splenosis mimicking a gastrointestinal stromal tumor (GIST) is rare. We present a case of a patient with a gastric SEL with growth concerning for a GIST that ultimately was diagnosed as ectopic splenic tissue (splenosis). This case highlights the importance of considering splenosis as a possible etiology for enlarging gastric SEL in patients with prior splenectomy. CASE DESCRIPTION/METHODS: A 52-year-old female with a remote history of solid pseudopapillary neoplasm (SPN) of the pancreas who received distal pancreatectomy and splenectomy 15 years ago presented with dyspepsia. 10 years ago, an esophagogastroduodenoscopy (EGD) revealed a 10-mm SEL in the gastric fundus. On endoscopic ultrasound (EUS) the lesion was described as a hypoechoic mass in the muscularis propria. Fine needle aspiration (FNA) was not performed given its challenging location. The patient opted for 4 years of annually computed tomography surveillance with stability of the lesion which was thought to be an accessory spleen. However, one year ago she presented to our clinic with dyspepsia. EUS revealed growth of the mass to 22.5 × 13.5 mm in the fourth layer with minimal vascularity suggestive of a GIST. Again, FNA was unsuccessful given its location in the greater curvature of the gastric fundus. Exploratory laparotomy was performed, the mass was excised, and pathology showed benign splenic tissue, consistent with splenosis. DISCUSSION: Splenosis and accessory spleen were considered initially as differential diagnoses in our patient given her splenectomy history. However, the indolent growth of the SEL and EUS appearance raised the concern of GIST. It is imperative to distinguish a GIST from other types of tumors to assess its malignant potential and treatment. Surgical excision was ultimately performed in our patient and the diagnosis of splenosis was made. Splenosis is a subtype of ectopic splenic tissue differentiated from accessory spleen, in that splenosis is acquired heterotopic autotransplantation and implantation of splenic tissue (usually after splenic trauma or splenectomy) while accessory spleen is a congenital anomaly with splenic arterial supply. Clinicians should be aware of the growth potential of splenosis as a mimicker of GISTs and other gastric SELs and consider ectopic splenic tissue a cause of SEL in patients without spleen.Figure 1.: EGD findings: Subepithelial nodule in the gastric fundus (year 0 vs year 9).Figure 2.: EUS findings (year 9): 22.5 × 13.5 mm well-defined hypoechoic and homogeneous mass arising from the fourth layer.Figure 3.: Histopathologic findings of subepithelial lesion: Benign splenic tissue, consistent with splenosis. (Hematoxylin-eosin x 100).