Endoscopic Ultrasound And High-resolution Melting Analysis For The Diagnosis In Gastrointestinal Stromal Tumors

Objiective:Gastrointestinal stromal tumors (GISTs) are submucosal lesions with overlying normal mucosal tissue. All GISTs have malignant potential. The preoperative diagnosis of GISTs is difficult. Morphologic examination and immunohistochemical staining for KIT or DOG-1, corroborated with the gastrointestinal anatomic location of the tumor, are essential for confirming GIST diagnosis. The pathogenesis of GIST are the exclusive mutations of the KIT and PDGFRA gene, which serve as crucial diagnostic and therapeutic targets. Endoscopic ultrasound (EUS) is the prime imaging modality when evaluating GISTs in stomach. High Resolution Melting Analysis (HRM or HRMA) is a recently developed technique for fast, high-throughput post-PCR analysis of genetic mutations. In this study, we examined whether EUS was useful in diagnosing GISTs. And we used a high-resolution melting (HRM) curve analysis approach to scan for mutations in the KIT and PDGFRA gene.Patients and methods:Gastric submucosal tumors were diagnosed from the immunohistochemical staining of specimens by excision at our hospital. All lesions underwent EUS preoperatively. Patients with small tumor (<2cm) and benign EUS features werw offered regular EUS surveillance. Hematoxylin and eosin-stained and immunohistochemistry was performed again in some GISTs. Stratifies risk of these tumors was established. HRM was used to detect mutations in the KIT and PDGFRA gene with postoperative freshly frozen tissue samples.Results:Among63gastric submucosal tumors,39GISTs were identified. The sensitivity, specificity, positive predictive value and negative predictive value of EUS for diagnosis of GISTs in stomach was100%,45.8%,75%and100%respectively. The median age of39GISTs patients was54years (range:34-77). Twenty-nine patients elected to undergo regular EUS surveillance for a mean periond of22±16.0months. Their median age was52years (range:31-71). None of patients showed internal increase in tumor size and change in EUS features.11gastric GISTs were established risk. All cases were positive for CD117, DOG-1and CD34. one case was regarded as very low risk,5cases were in the low risk,3case were in the intermediate risk and2cases were in the high-risk category. Three cases with5%-10%Ki-67staining positive cells were intermediate-high risk. Finally, we validated the HRM assay on12freshly frozen tissue samples. All mutated samples were correctly identified by HRM.10samples mutated in exon11of KIT gene could clearly be distinguished from the two wild-type samples. Among the ten mutated samples,9cases were from stomach and1cases was from intestine.Conclusion:(1) EUS has an advantage in evaluating the layer of origin of tumors and their internal architecture and is sensitive to diagnosis of GISTs in stomach.(2) For patients with small gastric GISTs (<2cm) with no high risk EUS features, EUS surveillance at12-to18-month intervals may be considered。(3) Elevated Ki-67scores were associated to high risk category and may be used as a putative prognostic marker.(4) HRM analysis is a powerful diagnostic tool for detection of KIT and PDGFRA gene mutation with a high sensitivity.