How are carcinoid tumors classified?

Updated: Feb 12, 2019
  • Author: Cameron K Tebbi, MD; Chief Editor: Max J Coppes, MD, PhD, MBA  more...
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Carcinoid tumors generally are classified based on the location in the primitive gut that gives rise to the tumor, as follows:

  • Foregut carcinoid tumors: Divided into sporadic primary tumors (lung, bronchus, stomach, proximal duodenum, pancreas) and tumors secondary to achlorhydria

  • Midgut carcinoid tumors: Derived from the second portion of the duodenum, the jejunum, the ileum, and the right colon

  • Hindgut carcinoid tumors: Includes the transverse colon, descending colon, and rectum

See Clinical Presentation for more detail.

Carcinoid tumors are divided into well-differentiated (i.e., low grade [ENETS G1] and intermediate grade [ENETS G2]) and poorly differentiated (i.e., high grade [ENETS G3]). Classification based on the extent of the tumor are local, regional and distant spread. (See grading and staging)

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