Mo1471 Diagnosis and KI-67 Grading of Pancreatic Neuroendocrine Tumors (pNETs): Role and Accuracy of Endoscopic Ultrasound-Fine Needle Aspiration (EUS-FNA)

(CB) from endoscopic ultrasound fine needle aspiration (EUS-FNA) offer a nonoperative means to assess tumor grade. Methods: 171 patients who had surgical resection for PNETs at CUMC from 1999 to 2012 were identified. IRB approval was obtained. Clinical and pathological data were collected. Patients who had both EUS-FNA CB and SRS available for review were included. Two pathologists reviewed all CB and SRS in blinded fashion. Immunohistochemical staining for Ki-67 was performed on whole mount slides of CB and SRS, which were assessed for Ki67 labeling index (percentage), intensity (weak, intermediate, or strong), and pattern (homogenous or heterogeneous). CB were also assessed for cellularity (scant or adequate). Statistical analyses using t-, Fisher’s exact, and kappa tests were performed using SAS 9.3. Results: 21 PNET patients with available CB and SRS were included. Mean age was 63.9+/10.2 years. Mean tumor size was 23.0+/13.5mm. 57.1% (12/21) had lymph node involvement and 50.0% (7/14) had invasive features. 40.0% (8/20) had mitotic rateR2 and 10% (2/20) had mitotic rateO10, per 50 high power field (HPF). For CB, WHO tumor grade was low (Ki67 index!3%) in 71.4% (15/21), intermediate (Ki67 index 3-20%) in 19.0% (4/21), and high (Ki67 index O20%) in 9.5% (2/21). For SRS, WHO tumor grade was low in 81.0% (17/21), intermediate in 9.5% (2/21), and high in 9.5% (2/21). 71.4% of observations were concordant, with weighted kappaZ0.47. Homogeneous Ki67 staining on SRS was significantly associated with CB-SRS concordance (pZ0.03). Where SRS had homogenous staining, concordance was 86.7%, with weighted kappaZ0.76. Classifying as low grade a tumor with Ki67 index up to 5%, which has been proposed, improved concordance to 91.3%, with weighted kappaZ0.83. As shown in Table 2, there was no significant relationship between CB Ki67 grade of intermediate or high (versus low) and clinical features, although analysis was limited by sample size. Conclusions: Prior small series compared EUS-FNA CB and SRS Ki67 indices in PNETs, but had discordant findings. Here we report the largest American series. We found a moderate correlation between CB and SRS Ki67 indices. The correlation was strongest with homogeneous Ki67 staining pattern. Staining was reliable even with scant CB cellularity. Our findings support the use of EUS-FNA Ki67 as a prognostic tool in helping to determine PNET management, including resection. Further studies are needed to determine whether increased EUS-FNA passes or different sampling techniques could feasibly improve the accuracy of tumor grading via endoscopy, especially in heterogeneously staining tumors.