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Colon tumor

Carcinoma

Small cell carcinoma of colon


Reviewers: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 25 February 2012, last major update January 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● < 1% of colorectal carcinomas
● Usually in right colon or cecum
● 30% arise from villous or other adenoma
● Mean age 63 years
● Poor prognosis due to early metastases to lymph nodes and liver, poor response to therapy
● 2/3 dead at 5 months historically (Am J Clin Pathol 1991;95:315)
● FNA may identify metastatic disease before known primary (Diagn Cytopathol 1996;15:54)

Comparison with metastatic pulmonary small cell carcinoma:
● CK8 is more sensitive than AE1 / AE3 or EMA for colonic small cell carcinoma
● TTF1 may be positive in small cell carcinoma of colonic origin, but most cases are negative (J Clin Pathol 2010;63:620)

Case reports
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● 44 year old woman with overlying villous adenoma (Arch Pathol Lab Med 2005;129:412)
● 67 year old woman with co-existing adenocarcinoma (Chirurg 2002;73:859)
● 70 year old man with rapid growth after resection (Tohoku J Exp Med 2006;209:361)
● 76 year old man with cecal tumor (Ann Diagn Pathol 2006;10:162)
● 76 year old man (Arch Pathol Lab Med 2001;125:1251)
● With ulcerative colitis (South Med J 1996;89:921)

Micro description
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● Resembles pulmonary tumor
● Sheets and nests of small round / ovoid cells with minimal cytoplasm, hyperchromatic nuclei with stippled chromatin, nuclear molding with peripheral palisading, usually brisk mitotic activity, apoptotic cells, necrosis and vascular invasion
● May have Azzopardi effect (encrustation of nuclear material around blood vessels)
● Adenoma present in 30-40%
● May have foci of glandular differentiation with variable mucin production or squamous differentiation
● No prominent nucleoli, no pleomorphism

Micro images
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H&E, synaptophysin


Left-H&E, right-synaptophysin


With overlying villous adenoma (D: synaptophysin+)

Positive stains
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● Neuron-specific enolase (84%), synaptophysin (50%), chromogranin (37%), leu7 (CD57, 18%)

E.M. description
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● Few dense-core secretory granules

End of Colon tumor > Carcinoma > Small cell carcinoma of colon


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