[1774] Intestinal Markers Are Expressed in Pancreatic Well-Differentiated Neuroendocrine Tumors and Associated with Sclerosing Variant

Adam S Johnson, Chanjuan Shi. Vanderbilt University Medical Center, Nashville, TN

Background: Recent literature has shown that cadherin 17 (CDH17) and CDX2 can be used as markers of gastrointestinal adenocarcinoma. However, such markers may not be unique to gastrointestinal tract-derived tumors. A small group of pancreatic well-differentiated neuroendocrine tumors (PanNETs) have a distinctive histology, characterized by a trabecular or trabecular-glandular cellular pattern with interspersed fibrosis and frequent expression of serotonin (sclerosing variant)—features commonly seen in small intestinal neuroendocrine tumors (SINETs). This study utilized tissue microarrays (TMAs) for analysis of CDH17 and CDX2 expression in PanNETs, including the sclerosing variant.
Design: Institutional approval was obtained for this study. Two TMAs containing 51 PanNETs and one TMA containing 29 SINETs were included in the study. Immunohistochemical labeling for CDX2 and CDH17 were performed on the TMAs. Pathology slides were also reviewed. Fisher's exact test was used for comparison.
Results: As expected, the vast majority of SINETs expressed the intestinal markers. Of the 29 SINETs, 27 showed diffuse and strong membranous expression of CDH17 (93%), and 23 showed nuclear expression of CDX2 (79%). All CDX2-positive SINETs were also labeled diffusely with CDH17. Some PanNETs also expressed the intestinal markers: 5 cases (5/51, 10%) expressing both markers, 16 (16/51, 31%) with only CDH17 expression and 3 (3/51, 6%) with only CDX2 expression. Among the 21 CDH17-positive tumors, the stain was diffuse and strong in 9 cases (9/51, 18%). Five of the 51 (10%) pancreatic tumors were sclerosing PanNETs, all of which (100%) had strong and diffuse expression of CDH17 and two (2/5, 40%) expressing CDX2. CDX2 and CDH17 were more commonly expressed in the sclerosing variant than other PanNETs (p<0.05).
Conclusions: Intestinal markers, CDH17 and CDX2, are expressed in a subset of PanNETs. Sclerosing PanNETs are associated with strong and diffuse expression of CDH17. CDH17 and CDX2 may not be used as markers to differentiate PanNETs from SINETs in patients with unknown primary NETs.
Category: Pancreas

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 270, Monday Morning


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