Endoscopic Management of Small GIST
Gastrointestinal stromal tumors (GISTs) comprise approximately 60–70 % of all masses identified in the GI tract. Approximately 5,000–6,000 new cases of GISTs arise in the United States each year, and of these, an estimated 30 % will become malignant. GIST
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Introduction
Gastrointestinal stromal tumors (GISTs) comprise approximately 60–70 % of all masses identified in the GI tract. Approximately 5,000–6,000 new cases of GISTs arise in the United States each year, and of these, an estimated 30 % will become malignant. GISTs are diagnosed via biopsy or resection and are stained for the KIT protein, also referred to as CD117. If the cells do not contain KIT, then they can be checked for the PDGFRA gene, which is found in approximately 5–10 % of GISTs [1]. They are often discovered incidentally during esophagogastroduodenoscopy (EGD) [2]. The National Institutes of Health (NIH) classifies low-risk and high-risk GISTs based on the size of the lesion, mitotic count, and proliferating cell nuclear antigen (PCNA) proliferative index (10 %). In order to completely assess the mitotic count, complete resection of the entire lesion may be required [3]. Some data suggest a higher incidence of subclinical GISTs than had been previously thought. In one study, 100 whole stomachs were resected from patients with gastric cancer and examined for microscopic GISTs. They found 50 microscopic GISTs, all of which were positive for KIT and/or CD34 and negative for desmin. Most microscopic GISTs (90 %) were located in the upper stomach [1, 4]. Another study found that microscopic gastric GISTs were present in 22.5 % of consecutive autopsies performed on patients aged 50 years or older [5] and a retrospective study
K.M. Nair, MD Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA F.F. Willingham, MD, MPH (*) Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA Department of Medicine, Emory University Hospital, 1364 Clifton Road, NE, Atlanta, GA 30322, USA e-mail: [email protected] © Springer International Publishing Switzerland 2017 C.R. Scoggins et al. (eds.), Gastrointestinal Stromal Tumors, DOI 10.1007/978-3-319-42632-7_8
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reported a prevalence of subepithelial gastric masses of 0.36 % during routine endoscopy [6]. Given the low reported annual incidence of clinical GISTs, presumably few microscopic GISTs are significant clinically. While GISTs are the most common tumor type, there are other submucosal tumors (SMTs) in the upper GI tract. Endoscopic ultrasound (EUS) plays a key role in the evaluation of submucosal tumors in the upper GI tract. EUS has the ability to assess the layer of origin, the depth of invasion, and via fine needle aspirates, can often provide a tissue diagnosis. Standard endoscopic techniques such as forceps biopsy often sample the overlying mucosal layer and are frequently unsuccessful in establishing a tissue diagnosis for submucosal tumors. Percutaneous biopsy is rarely appropriate as most smaller submucosal tumors are not well visualized by crosssectional imaging. In addition, there could be a small risk of tumor dissemination or rupture. Studies report the accuracy of EUS fine-needle aspiration (EUS-FNA) to be in the r
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