Colon tumor
Carcinoid tumors
Carcinoid - Rectum

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

Revised: 3 January 2017, last major update March 2016

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Carcinoid rectum [title]
Cite this page: Carcinoid - rectum. PathologyOutlines.com website. http://pathologyoutlines.com/topic/colontumorcarcinoid.html. Accessed May 24th, 2017.
Definition / general
Essential features
  • Most common carcinoid of colorectum
  • Good prognosis overall, but larger tumors can behave aggressively
  • Positive for neuroendocrine markers but also PSAP (a potential pitfall)
Terminology
  • Proper term is "rectal well differentiated neuroendocrine tumor"
Epidemiology
Sites
  • Rectum is most common site of well differentiated neuroendocrine tumor of colorectum; colon is less common
Pathophysiology
Diagnosis
Prognostic factors
Case reports
Treatment
Clinical images

Images hosted on other servers:

Small rectal carcinoids on colonoscopy

Gross description
  • Usually < 1 cm, round / polypoid, no ulceration
  • May appear yellow or pale
Microscopic (histologic) description
  • Islands, trabeculae, gland-like structures or sheets of monotonous neuroendocrine cells with amphophilic granular cytoplasm and round nuclei with "salt and pepper" chromatin
  • Usually minimal pleomorphism and little to no mitotic activity
  • Rarely mucin secretion or anaplasia; no necrosis
Microscopic (histologic) images

Images hosted on Pathout server - Contributed by Dr. Raul Gonzalez:

Small neuroendocrine tumor of the rectum

Synaptophysin positivity



Images hosted on other servers:

Rectal lesion

Small submucosal tumor

Rectal carcinoid and liver metastasis


Various images

Atypical carcinoid



Images hosted on Flickr:

Missing Image

Nested rectal carcinoid tumor

Chromogranin+ tumor

Negative stains
Electron microscopy description
  • Cytoplasmic, well formed membrane bound secretory granules with dense (osmophilic) cores
Molecular / cytogenetics description
  • Diploid if non metastasizing, aneuploid if metastatic
Differential diagnosis
  • Prostatic adenocarcinoma: positive for PSA, negative for neuroendocrine markers
  • Metastasis from other location: PAX8 is negative in ileal and pulmonary carcinoids, but positive in rectal carcinoid tumors
Additional references