Absence of L1 in pancreatic masses distinguishes adenocarcinomas from poorly differentiated neuroendocrine carcinomas

Background: Pancreatic adenocarcinoma is a tumor with fatal outcome. Cell adhesion molecules, such as L1 (CD171), have an essential function in tumor progression. L1 has been shown to be specifically expressed in poorly differentiated neuroendocrine carcinomas of the pancreas. The aim of this study was to determine the expression of L1 in pancreatic adenocarcinomas to evaluate whether L1 might differentiate between pancreatic carcinomas of neuroendocrine and ductal origin. Materials and Methods: L1 expression was retrospectively analyzed in 111 cases of pancreatic adenocarcinomas by immunohistochemistry on paraffin sections of primary tumors. Staining was performed by the peroxidase technique with monoclonal antibody against human L1. All tumors were classified according to the most recent TNM classification. Results: The focal expression of L1 was detected in 2 (2%) out of 111 pancreatic carcinomas only, the remaining 109 (98%) being L1-negative. No expression was found in acinar or ductal cells of normal pancreatic tissue. Conclusion: Our data suggest that L1 is expressed in few cases of pancreatic ductal adenocarcinoma. Since L1 was previously found to be expressed specifically in neuroendocrine pancreatic carcinomas, its absence in unclear pancreatic masses might hint at a ductal origin for a malignant pancreatic tumor.