A Retrospective Study on Safety, Diagnostic Yield and Therapeutic Effects of Endoscopic Unroofing for Small Gastric Subepithelial Tumors

INTRODUCTION

Small gastric subepithelial tumors (SETs) are often incidental findings at upper endoscopy. Differential diagnoses include a variety of different pathologies such as gastrointestinal stromal tumors (GISTs), leiomyomas, leiomyosarcomas, lipomas, carcinoid tumors, granular cell tumors, duplication cysts or pancreatic rests. Since some of these entities have a potential of malignancy, accurate classification of gastric SETs is essential to define the best diagnostic and therapeutic management. Endosonography (EUS) is the current gold standard for further characterization of small gastric SETs. It provides differentiation between extra- and intramural lesions, information on the involvement of certain wall layers, measurement of a lesion as well as structural analysis according to the echogenicity of a lesion. Nevertheless, a level of uncertainty remains, even if a lesion shows a typical echo-pattern and layer involvement.

According to current guidelines, lesions of more than two centimeters in size that are suspected to be GISTs should be removed by surgical resection. Lesions less than one centimeter can be followed by annual EUS. For lesions bigger than one centimeter but smaller than two centimeters tissue sampling is recommended in order to correctly diagnose a lesion according to immunohistochemical markers (such as CD117 or CD34 in GISTs) and to quantify the malignant potential according to other histological factors (such as the mitotic index in GISTs) [1].

Tissue sampling can be done by using standard or jumbo forceps biopsy and EUS-guided fine needle aspiration or biopsy, but the diagnostic yield of these methods is rather low [2,3]. Better results can be achieved by endoscopic resection techniques such as endoscopic submucosal dissection (ESD), submucosal tunneling endoscopic resection or full thickness endoscopic resection [4,5]. The main advantage of these approaches is that they are not only diagnostic but also therapeutic strategies since the respective lesion can be resected as a whole comparable with conventional surgery. However, there is a high risk of procedure related adverse events such as bleeding or perforation (the latter is often unavoidable considering that most SETs are arising from deep wall layers such as the muscularis propria layer).

Endoscopic unroofing is very similar to the mentioned endoscopic resection techniques with the main difference that only partial resection is intended in order to get a representative tissue specimen for histological evaluation. This method has been described in a case series by Lee et al. in 2010 where it showed a very favorable diagnostic yield in gastric SETs [6]. To date, no study has reported on the follow-up of lesions investigated by endoscopic unroofing.