Colon tumor
Carcinoid tumors
Carcinoid-colon but not rectum

Author: Raul Gonzalez, M.D. (see Authors page)

Revised: 25 May 2016, last major update May 2016

Copyright: (c) 2003-2016,, Inc.

PubMed Search: Carcinoid colon but not rectum
Cite this page: Carcinoid-colon but not rectum. website. Accessed December 11th, 2016.
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)
Clinical Images

Images hosted on other servers:

Endoscopic view of sigmoid WD-NET

Gross Description
  • Flat or depressed plaque or polyp
  • Yellow-tan, particularly after formalin fixation
Micro Description
  • Similar to WD-NET at other sites: islands, trabeculae or sheets of monotonous cells with pink-purple granular cytoplasm and round-oval stippled nuclei, small nucleoli, minimal pleomorphism, minimal mitotic activity, no necrosis
  • Rarely mucin secretion and anaplasia
Micro Images

Images hosted on Pathout server:

Contributed by: Raul S. Gonzalez, M.D., University of Rochester Medical Center (USA)

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)