Abstract
Pancreatic neuroendocrine tumors (PNETs) are a rare type of malignancy with a prognosis that is relatively good, compared with that of pancreatic adenocarcinoma. However, a number of patients with PNETs have distant metastasis and a less favorable prognosis. Epithelial-mesenchymal transition (EMT) is essential for tumor progression and metastasis. Snail and E-cadherin serve key roles in the process of EMT in numerous tumor types, including gastric and pancreatic adenocarcinoma. However, the role of EMT in PNETs remains unclear. The aim of the present study was to investigate the significance of Snail and E-cadherin expression in PNETs. Tissue samples were obtained from 40 resected PNETs. The expression of Snail and E-cadherin was evaluated in the primary tumors using immunohistochemical staining. The association between protein expression and patient clinicopathological features was then analyzed. High and low Snail expression levels were observed in 11 (27.5%) and 29 (72.5%) patients, respectively. Preserved and reduced E-cadherin expression was observed in 19 (47.5%) and 21 (52.5%) patients, respectively. Patients with low Snail expression and preserved E-cadherin expression had a significantly lower risk of vascular invasion, lymphatic invasion, lymph node metastasis and liver metastasis and a lower WHO classification, as compared with the group that included patients with high Snail and reduced E-cadherin, high Snail and preserved E-cadherin, and low Snail and reduced E-cadherin expression. In addition, the patients with low Snail expression levels and preserved E-cadherin expression had more a favorable prognosis compared with the other group. The present study indicates that EMT serves an important role in tumor progression in PNETs. Immunohistochemical evaluation of Snail and E-cadherin is useful for predicting the risk of vessel invasion and metastasis in PNETs.