Value of Islet 1 and PAX-8 in Identifying Metastatic Neuroendocrine Tumors of Pancreatic Origin.
Jamie Koo, Richard Mertens, Hanlin L Wang, Fai Chung, Deepti Dhall. Cedars-Sinai Medical Center, Los Angeles, CA
Background: Neuroendocrine tumors (NETs) can often present as metastases to the liver before the primary tumor is discovered. While the transcription factors TTF-1 and Cdx2 have been shown to aid in the identification of NETs of lung and gastrointestinal (GI) origin, respectively, no such marker has been established for the detection of NETs of pancreatic origin. Recently, two transcription factors, Islet 1 and PAX-8, have been proposed as markers for pancreatic NETs. The purpose of this study was to evaluate the usefulness of Islet 1 and PAX-8 in distinguishing metastatic pancreatic NETs from those originating from other primary sites, as well as to examine the sensitivity and specificity of TTF-1, Cdx2, Islet 1 and PAX-8 for metastatic NETs from a variety of primary sites.
Design: A total of 69 liver metastases of NETs with known primary sites were studied. The primary sites were established based on prior, concurrent or followup surgical pathology (53) or well documented clinical history (16). Immunohistochemistry was performed using antibodies against Islet 1, PAX-8, TTF-1 and Cdx2. Nuclear staining of at least 5% of tumor cells was considered a positive result. Staining intensity was also scored as weak, moderate or strong.
Results: Immunohistochemistry results are summarized below:
|Site of Primary||TTF-1||Cdx2||Islet 1||PAX-8|
|Pancreas (n=22)||1 (5%)||1 (5%)||0||16 (73%)||2 (9%)|
|Lung (n=7)||4 (57%)||0||0||1 (14%)||2 (29%)|
|Ileum (n=35)||0||8 (23%)||24 (69%)||0||0|
|Colon (n=2)||0||0||1 (50%)||0||0|
|Rectum (n=2)||0||0||0||2 (100%)||0|