Diagnostic yield of nonfunctional pancreatic neuroendocrine tumor using endoscopic ultrasound-guided fine needle aspiration biopsy

Abstract

e15680 Background: Radiological examinations including computed tomography (CT) and endoscopic ultrasound sonography (EUS) are important for the diagnosis of pancreatic neuroendocrine tumors (PNETs). Pathological diagnosis is not needed with functional PNETs because the diagnosis is made by biochemical testing. Therefore, pathological diagnosis is essential for the non-functional PNETs (nf-PNETs). In this study, we examined the diagnostic yield of radiological examinations and endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) for nf-PNETs. Methods: From January 1997 to December 2007, consecutive 38 cases were pathologically diagnosed from as nf-PNETs at Aichi Cancer Center Hospital. Of these 33 patients was diagnosed with surgical specimen, 5 patients with EUS-FNA specimen. Of 33 patients, 16 patients underwent EUS-FNA preoperatively, and were examined further: their EUS-FNA specimens were submitted for additional immunohistochemical examination for CD 56, chromogranin A, synaptophysin, somatostatin receptor 2A (SSTR2A) and Ki-67 using cell block method. Staging of PNETs was performed according to WHO classification. Results: 16 patients (10 men and 6 women) who ranged in age from 23 to 81 years. The mean of tumor size was 2.2 cm and ranged from 0.7 to 4.4 cm. Diagnosis by CT and EUS was 12 (75.0%) PNETs, two pancreatic cancer, one solid papillary tumors and one malignant lymphoma. Accurate diagnosis by cytology and immunohistochemistry was 75.0% and 93.8%, respectively. The Ki-67 in specimens of malignancy tended to be higher than those of benign or uncertain behavior. If we assumed that a tumor with Ki-67 of more than 2% was malignancy, the diagnostic accuracy was 75.0%. Positive reaction to SSTR2A was up to 14 out of 16 nf-PNETs. Conclusions: The EUS-FNA is a useful tool for diagnosing nf-PNETs with immunohistochemical staining compared to cytology and radiological examinations. Ki-67 may be also effective to predict the degree of malignancy. No significant financial relationships to disclose.