S2327 Single Incision Needle Knife (SINK) Biopsy for Diagnosis of a Large Gastric Subepithelial Lesion After Multiple Failed Fine Needle Aspirations

Abstract

INTRODUCTION: Subepithelial lesions (SELs) are a group of heterogenous tumors arising from layers below the gastrointestinal (GI) mucosa and are a common incidental finding on upper endoscopy. Although fewer than 15% of SELs are malignant, accurate diagnosis is essential to identify tumors that will need definitive management. Endoscopic ultrasound with fine needle aspiration (EUS-FNA) is an established technique frequently used to sample SELs, but diagnosis can still remain elusive in many instances. We present a case of a large gastric SEL where single incision needle knife (SINK) biopsy successfully produced a histopathologic diagnosis after multiple failed attempts with EUS-FNA. CASE DESCRIPTION/METHODS: A 66-year-old woman with epigastric pain, weight loss and early satiety underwent CT imaging that showed a 4.5 cm exophytic gastric mass. Initial EUS revealed a subepithelial, hypoechoic lesion with smooth borders and intraluminal convexity along the greater curvature of the stomach. It originated from the muscularis propria and measured 27 mm in depth. Two attempts with EUS-FNA at an outside hospital were non-diagnostic. At our center, EUS-FNA involving multiple passes with 22 and 25-gauge needles was also inconclusive. EUS was then repeated using the SINK biopsy technique. After exclusion of overlying vasculature and circumferential epinephrine injection, a 10 × 5 mm (length x depth) needle knife incision was made at the area of highest convexity over the lesion. A biopsy forceps was inserted into the defect for direct tissue sampling. Minor bleeding post-biopsy was treated with additional epinephrine and two hemostatic clips. A histologic diagnosis of GIST was made and the patient was referred for surgical resection as definitive management. DISCUSSION: This case highlights the limitations of EUS-FNA, while also providing further evidence to support SINK biopsy as a safe and effective technique. The reported yield for histologic diagnosis in upper GI SELs using SINK biopsy is between 81% and 92%. In cases with failed conventional biopsy or EUS-FNA, subsequent SINK biopsy has success rates ranging from 75% to 92%. No instances of perforation have been reported with SINK biopsy. As current ASGE guidelines do not endorse a standard biopsy method, the increased diagnostic yield and strong safety profile of SINK biopsy performed by experienced endoscopists suggests it should be the preferred technique over repeated EUS-FNA in cases of SELs with intraluminal convexity and prior non-diagnostic sampling.Figure 1.: Endoscopic Ultrasound (EUS) image of large gastric (greater curvature) subepithelial lesion arising from the muscularis propria with intraluminal convexity.Figure 2.: 10 × 5 mm (length x depth) incision of overlying mucosa using needle knife (Endo Cut).Figure 3.: Histology of sample obtained by SINK biopsy showing (A) proliferative and atypical spindle cells (hematoxylin and eosin, 20x), (B) positive DOG-1 staining (20x) and (C) positive C-KIT staining (20x).