[628] Well Differentiated Neuroendocrine Tumors of the Duodenum: A Clinicopathologic Profile and Somatostatin Receptor 2 Expression

Michael Alan Gilger, Lisa Cassani, Elizabeth Lindsey, Frank Revetta, Eric Liu, Chanjuan Shi. Vanderbilt University School of Medicine, Nashville, TN

Background: Duodenal neuroendocrine tumors (NETs) present as either functional or nonfunctional tumors. Based on the World Health Organization (WHO) grading system, duodenal NETs are further classified into grade 1 (G1) or grade 2 (G2) well-differentiated NET or grade 3 (G3, poorly differentiated) neuroendocrine carcinoma. Expression of somatostatin receptor 2 (SSTR-2) has been described in other NETs including pancreatic and small intestinal NETs. In this study, we examined 36 cases with duodenal NET and their expression of SSTR-2.
Design: Between 2003 and 2012, 36 patients with a diagnosis of duodenal NET were identified from our surgical pathology database. Demographics and clinical data were obtained from our electronic clinical database. Immunohistochemical (IHC) stains for Ki-67 and SSTR-2 expression were performed on paraffin-embedded formalin fixed tissue. The IHC results were interpreted by 2 pathologists.
Results: Of the 36 patients, 19 were males and 17 were females, with a mean age of 57.5 years (range 38 to 84 years). 46 total specimens were identified from the 36 patients; 24 cases were biopsies, 13 were Whipple resections, and 9 were local excisions. 13.9% of patients (5/36) had functional tumors, 4 of these were gastrinomas and 1 was a somatostatinoma. 52.8% of patients (19/36) were symptomatic while 47.2% (17/36) were incidental findings. 7% (4/36) patients had an associated diagnosis of multiple endocrine neoplasia syndrome – type I. Of cases with endoscopic data available, 54.5% (12/22) were nodules, 40.9% (9/22) were polyps, and 4.6% (1/22) was an ulcer. There were 23 G1, 12 G2, and 1 G3 based on mitotic rate and Ki-67 proliferative index. Out of the 5 functional tumors, 2 were G1, 2 were G2, and 1 was G3. SSTR-2 staining in a membranous pattern was observed overall in 33/36 (91.7%) of cases. Staining was observed in 87.0% of G1 (20/23), 100% of G2 (12/12), and 100% of G3 (1/1). 4 of the 5 (80%) functional tumors expressed SSTR-2.
Conclusions: The majority of duodenal NETs are well-differentiated and non-functional. SSTR-2 shows strong membranous staining in over 91% of duodenal NETs. SSTR-2 can be potentially used in cancer imaging and targeted therapeutic strategies for duodenal NETs.
Category: Gastrointestinal

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 114, Tuesday Afternoon


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