Immunohistochemistry for cell polarity protein lethal giant larvae 2 differentiates pancreatic intraepithelial neoplasia-3 and ductal adenocarcinoma of the pancreas from lower-grade pancreatic intraepithelial neoplasias.

Pancreatic intraepithelial neoplasia is a precursor to ductal adenocarcinoma of the pancreas that shows gastric differentiation. Pancreatic intraepithelial neoplasia-3 has the highest potential to progress to adenocarcinoma, and its distinction from lower-grade pancreatic intraepithelial neoplasias is important for clinical management. However, morphologic grading of pancreatic intraepithelial neoplasia suffers from significant interobserver variability. A product of cell polarity gene lethal giant larvae 2 is a marker of gastric foveolar epithelium expressed in a basolateral fashion, which is lost or mislocalized in gastric epithelial dysplasia and adenocarcinoma. In this study, we investigated a role of lethal giant larvae 2 expression in differentiating low-grade pancreatic intraepithelial neoplasias, that is, pancreatic intraepithelial neoplasia-1 and pancreatic intraepithelial neoplasia-2, from pancreatic intraepithelial neoplasia-3 and pancreatic ductal adenocarcinoma. The immunohistochemical patterns of lethal giant larvae 2 expression were examined in normal pancreatic ducts, 48 pancreatic intraepithelial neoplasia lesions of all histologic grades, and 91 adenocarcinomas on a tissue microarray or conventional sections. The expression pattern was recorded as basolateral, cytoplasmic, negative, or combinations of any of them. Whereas normal duct epithelia did not exhibit lethal giant larvae immunoreactivity, all but one lesion of low-grade pancreatic intraepithelial neoplasia showed basolateral lethal giant larvae staining. Conversely, all lesions of pancreatic intraepithelial neoplasia-3 and adenocarcinoma showed loss of lethal giant larvae 2 staining and/or its cytoplasmic localization. Interestingly, a basolateral expression was focally seen in 4 adenocarcinomas with a foamy gland pattern and was always admixed with negatively stained areas. In conclusion, our results show that low-grade pancreatic intraepithelial neoplasias express lethal giant larvae 2 in a basolateral fashion recapitulating expression in normal gastric epithelium. Loss or abnormal lethal giant larvae 2 expression is seen in pancreatic intraepithelial neoplasia-3 and adenocarcinoma and might be useful in separating them from lower-grade pancreatic intraepithelial neoplasias.