One of the first things to learn about NETs is that no two tumors are alike. Doctors o en say these tumors are “heterogeneous,” meaning the NETs can vary by site, how fast they grow, and whether they cause symptoms.
NETs can occur almost anywhere in the body, but most commonly start in the gastrointestinal (GI) tract, lung, or pancreas.
The place where a NET first forms is called the primary site. From its primary site, a NET can spread to other places, such as the lymph nodes or the liver. When a tumor spreads, it is called metastasis.
Sometimes testing will show where neuroendocrine cancer has spread in the body but not where the tumor started (the “primary site”). In such a case, the cancer is said to be of “unknown primary.”
The signs and symptoms for NETs vary depending on the primary site of a tumor.