Light micrograph of a section through human pancreatic tissue showing pancreatic neuroendocrine tumour (pNET). This refers to a group of cancers that can occur in the hormone-producing cells of the pancreas, a rare disease also known as islet cell cancer. Some pancreatic neuroendocrine tumour cells continue to secrete hormones (known as functional tumours), creating too much of a given hormone in the body. Examples of these include gastrinoma and glucagonoma. Sometimes these tumours do not secrete an excess amount of these hormones (known as non-functional tumours).