Neuroendocrine tumors

Neuroendocrine carcinoma

Last author update: 2 February 2021
Last staff update: 4 October 2023

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PubMed Search: Neuroendocrine carcinoma [title] colon

Raul S. Gonzalez, M.D.
Page views in 2023: 21,668
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Cite this page: Gonzalez RS. Neuroendocrine carcinoma. website. Accessed February 26th, 2024.
Definition / general
Essential features
  • Large cell or small cell neuroendocrine carcinoma
  • Rare and aggressive (distant metastases common, with poor survival rate)
  • Histology similar to neuroendocrine carcinomas elsewhere
  • Full proper term is poorly differentiated neuroendocrine carcinoma
  • 2 subtypes, based on morphology: large cell neuroendocrine carcinoma and small cell carcinoma
  • Usually in cecum or right colon but can arise anywhere
  • Disease typically presents at advanced stage
Clinical features
Prognostic factors
  • Good prognostic factors include peritumoral lymphocytes, microsatellite instability and pure large cell features; poor prognostic factors include CD117 positivity and vascular invasion (Am J Surg Pathol 2012;36:601)
  • Slightly improved prognosis if disease is not metastatic or patient responds to chemotherapy (Ann Surg Oncol 2014;21:2956)
Case reports
Radiology images

Images hosted on other servers:
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Rectal mass

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Noncontrast CT scans of abdomen

Microscopic (histologic) description
  • Large cell:
    • Organoid arrangement of cells larger than those in small cell carcinoma, with nuclear pleomorphism and hyperchromasia, prominent nucleoli, numerous mitoses and tumor necrosis
  • Small cell:
    • Resembles pulmonary small cell carcinoma, with sheets and nests of small ovoid cells with minimal cytoplasm, hyperchromatic nuclei with stippled chromatin, nuclear molding with peripheral palisading, brisk mitotic activity, apoptotic cells, necrosis and vascular invasion
    • No prominent nucleoli or pleomorphism
    • May have Azzopardi effect (encrustation of nuclear material around blood vessels)
Microscopic (histologic) images

Contributed by Raul S. Gonzalez, M.D., Aaron Huber, D.O. and Diana Agostini-Vulaj, D.O. (Case #531)
Large cell neuroendocrine carcinoma Large cell neuroendocrine carcinoma

Large cell neuroendocrine carcinoma




Positive stains
Electron microscopy description
  • Dense core secretory granules
Sample pathology report
  • Sigmoid colon, resection:
    • Poorly differentiated neuroendocrine carcinoma (see synoptic report and comment)
    • Comment: The tumor demonstrates large cell neuroendocrine carcinoma morphology. Immunostains show the tumor is positive for synaptophysin and chromogranin, with a Ki67 index of 85%. By definition, neuroendocrine carcinomas are WHO grade 3.
Differential diagnosis
Board review style question #1
    Which of the following is true about neuroendocrine carcinomas of the colorectum?

  1. Large cell and small cell subtypes have differences in prognosis and clinical management
  2. They are positive for synaptophysin but negative for chromogranin
  3. They can be any WHO grade
  4. They present at a younger average age than colorectal adenocarcinoma
Board review style answer #1
D. They present at a younger average age than colorectal adenocarcinoma

Comment Here

Reference: Neuroendocrine carcinoma
Board review style question #2
    A colorectal tumor is resected and appears to be a poorly differentiated adenocarcinoma, with focal but convincing gland formation. A synaptophysin immunostain is performed and shows patchy scattered positive staining in about 5% of cells. How should this tumor be diagnosed?

  1. Mixed neuroendocrine nonneuroendocrine neoplasm
  2. Poorly differentiated adenocarcinoma
  3. Poorly differentiated neuroendocrine carcinoma (large cell neuroendocrine carcinoma)
  4. Poorly differentiated neuroendocrine carcinoma (small cell carcinoma)
Board review style answer #2
B. Poorly differentiated adenocarcinoma

Comment Here

Reference: Neuroendocrine carcinoma
Board review style question #3
    Which of the following is true of poorly differentiated neuroendocrine carcinoma, large cell type in the colon?

  1. INSM1 expression is a sensitive and specific immunohistochemical marker for neuroendocrine differentiation
  2. Mixed neuroendocrine nonneuroendocrine neoplasm may be diagnosed if the poorly differentiated neuroendocrine carcinoma comprises only 5% of the total tumor volume
  3. This tumor has an overall good prognosis
  4. This tumor is a common morphologic subtype of colorectal cancer
Board review style answer #3
A. INSM1 (insulinoma associated protein 1) is a sensitive and specific marker of neuroendocrine differentiation in neuroendocrine neoplasms. Answer B is incorrect because the WHO criteria for mixed neuroendocrine nonneuroendocrine neoplasm requires at least 30% of each component. Answers C and D are incorrect because LCNEC of the colon is a rare highly aggressive subtype of colorectal cancer with a poor prognosis. See Case #531 for more information.

Comment Here

Reference: Neuroendocrine carcinoma
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