1.2. Pancreatic masses Pancreatic solid masses can be either exocrine or endocrine tumors, or metastatic.Exocrine tumors are by far the most common type of pancreas cancer. Most of them are malignant. About 96% of cancers of the exocrine pancreas are adenocarcinomas, which is the most aggressive form of pancreas cancer.Endocrine tumors are uncommon. They represent 4% of pancreas tumors. They are known as neuroendocrine tumors (NETs), or islet cell tumors. These tumors can be benign or malignant.