Colon tumor
Neuroendocrine neoplasms
Carcinoid - colon but not rectum

Topic Completed: 1 May 2016

Minor changes: 23 May 2020

Copyright: 2003-2019,, Inc.

PubMed Search: Carcinoid colon but not rectum

Raul S. Gonzalez, M.D.
Page views in 2019: 2,697
Page views in 2020 to date: 772
Cite this page: Gonzalez R. Carcinoid - colon but not rectum. website. Accessed May 28th, 2020.
Definition / general
  • Well differentiated neuroendocrine lesion arising in the cecum or colon (but not the appendix or rectum)
Essential features
  • Colon is least common site for intestinal carcinoids
  • Prognosis is worse than for most other intestinal sites
  • Proper term is well differentiated neuroendocrine tumor (WD-NET)
  • May arise as part of a tubular adenoma; current term for these indolent lesions is "composite intestinal adenoma - microcarcinoid' (Am J Surg Pathol 2012;36:292)
  • Colon proper is the least common site for intestinal WD-NET
Clinical features
Case reports
  • 58 year old man with composite intestinal adenoma - microcarcinoid (Case of Week #189)
Gross description
  • Flat or depressed plaque or polyp
  • Yellowish tan, particularly after formalin fixation
Microscopic (histologic) description
  • Similar to WD-NET at other sites: islands, trabeculae or sheets of monotonous cells with pinkish purple granular cytoplasm and round or oval stippled nuclei, small nucleoli, minimal pleomorphism, minimal mitotic activity, no necrosis
  • Rarely mucin secretion and anaplasia
Microscopic (histologic) images
Contributed by Raul S. Gonzalez, M.D.

WD-NET of ascending colon

Positive stains
Electron microscopy description
  • Well formed membrane bound secretory granules with dense (osmophilic) cores
Differential diagnosis
Additional references
  • eMedicine (general overview of gastrointestinal WD-NETs)
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