Various types of neuroendocrine tumors (NET) may form in many places in the body and grow differently. Many NETs first appear in the lungs or the gastrointestinal tract, including the stomach, pancreas, appendix, intestines, colon and rectum. NETs may also appear in the thymus, thyroid gland, adrenal gland and pituitary gland.
NETs may be classified by the site of origin. Doctors may use terms such as GI NET, pancreatic NET or lung NET to describe the tumor. Although NETs vary in size and how quickly they grow, almost all NETs are considered malignant, or cancerous.
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