Anus & perianal area
Carcinoma
Small cell (neuroendocrine) carcinoma


Topic Completed: 31 March 2021

Minor changes: 21 April 2021

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

Raul S. Gonzalez, M.D.
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Cite this page: Gonzalez RS. Small cell (neuroendocrine) carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/anussmallcell.html. Accessed May 6th, 2021.
Definition / general
  • Poorly differentiated neuroendocrine carcinoma arising in the anus
Essential features
  • Rare primary neuroendocrine carcinoma of the anus
  • Very aggressive, with early metastatic spread; 5 year survival approximately 10%
  • Similar histology to small cell carcinoma at other sites
Epidemiology
Pathophysiology
Radiology images

Images hosted on other servers:

MRI

PET scan

Metastatic disease

Case reports
Treatment
  • Chemotherapy and radiation
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

Contributed by Raul S. Gonzalez, M.D.
Small cell carcinoma Small cell carcinoma

Small cell carcinoma

Large cell carcinoma Large cell carcinoma

Large cell carcinoma



Images hosted on other servers:

Small cell carcinoma

Small cell carcinoma

Positive stains
Negative stains
  • CDX2 (positive in rectal small cell carcinomas)
Sample pathology report
  • Anus, mass, biopsy:
    • Small cell neuroendocrine carcinoma (see comment)
    • Comment: The carcinoma is positive for synaptophysin and chromogranin by immunohistochemistry. Neuroendocrine carcinomas are high grade by definition.
Differential diagnosis
Board review style question #1

This primary anal lesion is positive for pankeratin. What other stain would be expected to be positive?

  1. CD45
  2. CDX2
  3. Napsin A
  4. Synaptophysin
Board review style answer #1
D. Anal small cell carcinoma, like all neuroendocrine carcinomas, is positive for synaptophysin.

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Reference: Small cell (neuroendocrine) carcinoma
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