[599] Immunohistochemical Expression of ER, PR and Ki67 in Pancreatic and Small Intestinal Neuroendocrine Tumors

AT Arnason, PJ Barnes, D Rayson, M Drewniak, HL Sapp. Dalhousie University, Halifax, NS, Canada

Background: There has been limited study of ER and PR expression in GI neuroendocrine tumors (GI NETs) despite emerging evidence for hormone receptor regulation of pancreatic islet cells. Normal pancreatic islet cells express PR and progesterone has been implicated in the pathogenesis of gestational diabetes. Islet cell proliferation has been demonstrated in PR gene knockout mice. Additionally, a recent study has shown frequent ER and PR expression in primary lung NETs. Investigation of ER and PR expression in GI NETs is therefore warranted.
Design: Pathology records were searched to identify patients who had a GI NET diagnosed from Sept. 1991 to Jan. 2009. An IHC panel including Ki67, ER, and PR was applied to tissue microarrays for 74 primary resections and to 9 biopsy specimens. ER and PR were interpreted as negative, 1+ (weak intensity and/or <75% of cells) or 2+ (moderate or strong intensity and >75% of cells).
Results: IHC results for 83 cases (38 male, 45 female, mean age 60 years) are summarized below.

SiteER -ER +PR -PR +Ki67<2%Ki67>2%
SI (non-duodenal) [n=31]13 (42%)18 (58%)26 (84%)5 (16%)28 (90%)3 (10%)
Duodenum [n=9]7 (78%)2 (22%)1 (11%)8 (89%)5 (56%)4 (44%)
Pancreas [n=43]37 (86%)6 (14%)11(26%)32 (74%)33 (77%)10 (23%)
Number (%) of cases showing ER/PR expression (negative [-], positive 1+ or 2+ [+]) and Ki67 index according to primary site.

Small intestinal (non-duodenal [SI]) NETs were significantly more likely to express ER than pancreatic primaries (58% vs 14%, p<0.001). Pancreatic NETs were more likely to be PR + than SI tumors (74% vs. 16%, p<0.001). Duodenal tumors showed similar ER/PR expression to pancreatic NETs, however, only the PR + frequency was significantly different from other SI sites (89% vs. 16%, p<0.001). Only pancreatic (25) and duodenal (4) primaries showed 2+ PR staining. There was more frequent 2+ PR staining (p<0.001) in WHO Class 1 pancreatic NETs (20/23=87%) compared to Class 2&3 NETs (5/20=25%). Ki67 was more often >2% (p<0.01) in WHO Class 2&3 tumors (9/20=45%) than in WHO Class 1 tumors (1/23=4%). There was a non-significant trend towards metastasis in duodenal tumors without 2+ PR and with Ki67>2%. There was a non-significant trend towards increased ER expression and Ki67>2% in SI tumors with metastates.
Conclusions: SI NETs show a distinct ER/PR expression profile from pancreatic and duodenal primaries. Pancreatic NETs with strong PR expression (2+) are less likely to show metastatic behavior.
Category: Gastrointestinal

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 86, Monday Morning


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