The Features and Accuracy of Endosonography (EUS) On Diagnosis of Gastroduodenal Carcinoid Tumors

Abstract

Background: Gastroduodenal carcinoid tumors are rare, indolent neuroendocrine tumors, identified incidentally during endoscopy for upper GI symptoms although some present as a bleeder. EUS is a sensitive method in the detection of gastroduodenal carcinoid, but the interobserver agreement was poor for carcinoid in diagnosis of subepithelial tumors (SET) even to experienced endosonographers. Aims: To evaluate the features and diagnostic accuracy of high-frequency ultrasound probe (HFUP) on gastroduodenal carcinoid tumors from other SETs. Methods: From Jan.2002 to Jul.2008, there were 65 patients with polyp or SETs, identified as suspected gastric or duodenal carcinoids by HFUP (Olympus UM-2R/3R) from EUS database of one institute (CGMH). After excluding tumors from muscularis propira, papillary location, and without histologic diagnosis, a total of 49 cases (stomach 28, duodenum 21) were analyzed retrospectively on EUS images/video, blind to final clinopathological outcomes. The Fisher's exact and The Mann-Whitney U-test was also used to compare the categorical and continuous variables. Results: There were total 20 patients (M: F=12: 8), mean age 57.5 yrs (39-84 yrs) with carcinoid tumors (gastric 10, duodenal 10), confirmed by endoscopic biopsy or resection. The size of carcinoid tumor is 7.6 mm +/-3.7 mm (mean +/- SD) on stomach, and 7.2 mm +/- 2.4 mm on duodenum. The three common EUS features included: distinct margin (75%), homogeneous hypoechoic lesion (80%) and deep mucosa to submucosal location (70%). Applying these EUS features (at least 2 criteria) for diagnosis of carcinoid tumors on all 49 cases, the positive predictive value is 62% and the negative predictive value is 83%, accuracy 71%. Comparing the tumor location showed: gastric body, 90% on carcinoid group, 33% on other gastric SETs (P=0.005); Duodenal bulb, 100% on carcinoid group, 27% on other duodenal SETs (P<0.001). Pathology of the misdiagnosed 29 SETs included: 9 ectopic pancreas, 8 inflammations, 3 GIST, 2 lipomas, 2 cysts, 1 MALT lymphoma, 1 Brunner's gland adenoma, 1 polyp. 2 undiagnosed lesion. Their mean sizes are 10.9mm +/- 6.1mm (stomach) and 9.2 mm +/- 3.4mm (duodenum). Conclusions: Most of gastroduodenal carcinoid tumors are less than 10 mm in size, with well-defined margin and hypoechoic nature in deep mucosal and submucosal layers. Tumor locations (eg. proximal stomach and duodenal bulb) are good predictive factors on differential diagnosis in addition to EUS features.