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Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Sites | Clinical features | Case reports | Clinical images | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Electron microscopy description | Differential diagnosis | Additional referencesCite this page: Carcinoid - colon but not rectum. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colontumorcarcinoidnotrectum.html. Accessed July 14th, 2017.
Definition / general
Essential features
- Colon is least common site for intestinal carcinoids
- Prognosis is worse than for most other intestinal sites
Terminology
- 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)
Epidemiology
- Colon proper is the least common site for intestinal WD-NET
Sites
- Cecum and ascending colon most common site for colonic WD-NET (Clin Colon Rectal Surg 2006;19:45)
Clinical features
- More common in women (Am J Surg 1985;149:775)
- Carcinoid syndrome occurs in ~ 5% of patients
- Average tumor size is 5 cm, and more than 2/3 of cases are metastatic at presentation (N Engl J Med 1999;340:858)
- 5 year survival is ~ 62% (Cancer 2003;97:934)
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
- 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
Images hosted on Pathout server:
Images contributed by Raul S. Gonzalez, M.D.
WD-NET of ascending colon
Positive stains
- Synaptophysin and chromogranin
- Ki67 should be performed to grade lesion, per WHO guidelines
Electron microscopy description
- Well formed membrane bound secretory granules with dense (osmophilic) cores
Differential diagnosis
- Colonic poorly differentiated neuroendocrine carcinoma: high grade with anaplasia, necrosis, numerous mitoses
- Small cell carcinoma or large cell neuroendocrine carcinoma
Additional references
- eMedicine (general overview of gastrointestinal WD-NETs)
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