Neuroendocrine Tumor Descriptors
Functional and Non-Functional Tumors
Neuroendocrine tumors may be functional or nonfunctional, depending on their hormone secretion.
Functional NETs produce excess hormones, while nonfunctional tumors don’t produce hormones or enough of them to cause noticeable symptoms. Which hormone or hormones the cancer cells secrete depend on where the cancer develops. About 60 percent of NETs are categorized as nonfunctional, according to the American Society of Clinical Oncology (ASCO). The symptoms of neuroendocrine cancer—if you have any—and the treatment plan will likely depend on whether the tumor is functional or nonfunctional.
Indolent and Aggressive Tumors
Neuroendocrine cancer can be indolent or aggressive. Both indolent and aggressive neuroendocrine cancer has the ability to spread and metastasize to other parts of the body.
An indolent neuroendocrine tumor (NET) is a slow-growing, with cells that look somewhat similar (well-differentiated) to normal, noncancerous cells. This is also called a low-grade NET. There’s a lower risk of spread, or metastasis, with indolent NETs.
An aggressive NET is a fast-growing tumor, with cells that are poorly differentiated, meaning they look very different from normal, noncancerous cells. There's a higher risk of spread, or metastasis, with aggressive NETs.
Because aggressive NET cells are so different from normal non-cancerous cells, chemotherapy may be more successful against them. Indolent NET cells may not respond as well to treatment due to their similarity to normal cells.