Tissue-specific cadherin CDH17 is a useful marker of gastrointestinal adenocarcinomas with higher sensitivity than CDX2.

Cadherin 17 (CDH17) is a cell adhesion molecule expressed in intestinal epithelium and transcriptionally regulated by CDX2. We compared the usefulness of CDH17 as an immunohistochemical intestinal marker to that of CDX2 in gastrointestinal and extragastrointestinal carcinomas and nonneoplastic tissues. Nonneoplastic intestinal and pancreatic duct epithelia were CDH17-positive. Most esophageal (79%), gastric (86%), and colonic (99%) adenocarcinomas were CDH17-positive/CDX2-positive, whereas 1% of colonic, 18% of esophageal, and 10% of gastric adenocarcinomas were CDH17-negative/CDX2-negative. Rare colonic, esophageal, and gastric adenocarcinomas were CDH17-positive/CDX2-negative (1%, 3%, and 4%, respectively), and none were CDH17-negative/CDX2-positive. Diffuse CDH17 was also observed in all metastatic colon carcinomas, 20% of which were only focally CDX2-positive. Of intestinal low-grade neuroendocrine tumors, 74% coexpressed CDX2 and CDH17. CDH17 was also positive in 12% of pancreatic and 24% of bronchial neuroendocrine tumors, all of which were CDX2-negative. Pancreatic adenocarcinomas and cholangiocarcinomas were more frequently CDH17-positive than CDX2-positive (50% vs 27%, 53% vs 27%). One (2%) hepatocellular carcinoma was CDH17-positive/CDX2-negative. Nine percent of non-small cell lung cancers and 7% of endometrial carcinomas were CDH17-positive, whereas 3% of lung, 5% of endometrial, 3% of ovarian, and 2% of breast carcinomas were CDX2-positive. Thus, CDH17 is slightly more sensitive than CDX2 when detecting gastrointestinal adenocarcinomas.