Anus & perianal area
Small cell (neuroendocrine) carcinoma

Topic Completed: 1 December 2014

Minor changes: 16 November 2020

Copyright: (c) 2002-2021,, Inc.

PubMed Search: small cell carcinoma anus "loattrfree full text"[sb]

Raul S. Gonzalez, M.D.
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Cite this page: Gonzalez RS. Small cell (neuroendocrine) carcinoma. website. Accessed January 22nd, 2021.
Definition / general
  • Poorly differentiated neuroendocrine carcinoma arising in the anus
  • Rare and very aggressive, with early metastatic spread; 5 year survival approximately 10%
Case reports
  • Chemotherapy and radiation
Clinical images

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PET scan

Metastatic disease

Microscopic (histologic) description
  • Poorly differentiated neuroendocrine tumor composed of solid nests of small cells with minimal cytoplasm, hyperchromatic nuclei with molding, central necrosis and high mitotic activity
  • Resembles pulmonary counterpart
  • May have overlying squamous cell carcinoma in situ (Pathol Int 2012;62:356)
Microscopic (histologic) images

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Small cell carcinoma

AE1 / 3, p63

High grade

Positive stains
Negative stains
  • CDX2 (positive in rectal small cell carcinomas)
Differential diagnosis
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