Colon tumor
Carcinoma
Adenocarcinoma of colon

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

Revised: 23 November 2015, last major update November 2015

Copyright: (c) 2002-2015, PathologyOutlines.com, Inc.

PubMed Search: Adenocarcinoma [title] colon
Cite this page: Adenocarcinoma of colon. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colontumoradenocarcinoma.html. Accessed December 3rd, 2016.
Definition / General
Essential Features
  • Most common primary colon carcinoma
  • Typically arises through chromosomal instability pathway (70-80%) or microsatellite instability pathway (10-15%)
  • Stage is most important prognostic factor
Clinical Features
  • Increased carcinoma risk in patients with polyposis syndromes, Lynch syndrome and inflammatory bowel disease
  • Right sided tumors cause anemia, weakness and fatigue
  • Left sided tumors cause change in bowel habits (diarrhea or constipation)
  • Superficial tumors only rarely cause lymph node metastases due to distribution of lymphatics in colon
Diagnosis
  • Generally discovered on colonoscopy and confirmed on biopsy
Prognostic Factors
  • Poor prognostic factors include advanced stage, higher grade and positive margins
  • Tumor budding is linked to worse outcome (Mod Pathol 2012;25:1315)
Case Reports
Treatment
  • Surgical resection is generally required unless tumor is small and confined to a polyp
  • Adjuvant therapy given for patients with lymph node metastases
  • Neoadjuvant therapy often given for rectal carcinomas
Clinical Images
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Colon cancer, colonoscopy

Gross Description
  • Usually single, polypoid or ulcerated mass
  • May cause serosal puckering if muscularis propria is involved
  • Right colon tumors tend to be polypoid and exophytic, while left colon tumors tend to be annular, encircling lesions
Gross Images

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Early, flat tumor

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Flat, small adenocarcinoma

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Invasive mucinous adenocarcinoma

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Exophytic lesion

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Napkin ring lesion

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Invasion via muscularis propria

Micro Description
  • Usually well or moderately differentiated gland forming carcinoma with marked desmoplasia, particularly at edge of tumor
  • Glands often filled with necrotic debris ("dirty necrosis"), in both primary and metastatic sites
  • Inflammatory cells and scattered neuroendocrine cells are common (Pol J Pathol 2005;56:89)
  • Intramural venous invasion may be easier to identify using an elastin stain (J Clin Pathol 2002;55:17)

  • Well differentiated:
    • 15 - 20% of all carcinomas
    • Well formed glands or simple tubules with uniform, basally oriented nuclei
    • Somewhat resembles adenomatous epithelium
  • Moderately differentiated:
    • 60 - 70% of all carcinomas
    • Tubules may be simple, complex or slightly irregular
    • Nuclear polarity lost
  • Poorly differentiated:
    • 15 - 20% all of carcinomas
    • Less than 50% gland formation
    • Majority of tumor (excluding advancing edge) consists of sheets of cells without gland formation
    • Usually right sided (Hepatogastroenterology 2004;51:1698)
  • Note: pre-operative histologic grading is not accurate (J Med Assoc Thai 2005;88:1535)
Micro Images

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Whole mount scan

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Moderately differentiated

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Mucinous and undifferentiated areas

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"Dirty necrosis" in gland lumens

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Venous invasion

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Serosal penetration

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Detached carcinoma cells

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Signet ring morphology

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Lymph node metastasis

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Courtesy of Dr. Semir Vranic, University of Sarajevo (Bosnia)

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C/o Dr. Beverly Wang, Beth Israel Medical Center

Negative Stains
Molecular / Cytogenetics Description
  • Most commonly mutated genes include APC, TP53, and KRAS
  • Molecular classification of carcinomas has been proposed (Histopathology 2007;50:113)
  • Tumors can be screened for microsatellite instability via immunohistochemistry for MLH1, MSH2, MSH6 and PMS2
Videos



Differential Diagnosis