Colon

Carcinoma

Adenocarcinoma


Editorial Board Member: Catherine E. Hagen, M.D.
Raul S. Gonzalez, M.D.

Topic Completed: 10 May 2021

Minor changes: 10 May 2021

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PubMed Search: Adenocarcinoma[TI] colon[TI] review[PT]

Raul S. Gonzalez, M.D.
Page views in 2020: 40,165
Page views in 2021 to date: 42,421
Cite this page: Gonzalez RS. Adenocarcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumoradenocarcinoma.html. Accessed October 21st, 2021.
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
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
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

Microscopic (histologic) description
  • Usually well or moderately differentiated gland forming carcinoma with marked desmoplasia, particularly at edge of tumor
  • Glands often cribriform and 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: preoperative histologic grading is not accurate (J Med Assoc Thai 2005;88:1535)
Microscopic (histologic) images

Contributed by Raul S. Gonzalez, M.D.

Low power

High power

Dirty necrosis

Dirty necrosis

Cribriforming

Cribriforming

Desmoplasia

Desmoplasia

Lymphovascular invasion

Lymphovascular invasion



Contributed by Semir Vranic, M.D., Ph.D. and Beverly Wang, M.D.

Poorly differentiated adenocarcinoma

Adenocarcinoma



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Whole mount scan

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Moderately differentiated

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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

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

Histopathology colon adenocarcinoma

Sample pathology report
  • Sigmoid colon, resection:
    • Adenocarcinoma, moderately differentiated (see synoptic report)
Differential diagnosis
Board review style question #1
    Which of the following is an official WHO recognized subtype of colorectal adenocarcinoma (per the 2019 classification)?

  1. Adenosquamous carcinoma
  2. Clear cell carcinoma
  3. Cribriform comedo carcinoma
  4. Low grade tubuloglandular adenocarcinoma
Board review style answer #1
A. Adenosquamous carcinoma

Comment Here

Reference: Adenocarcinoma
Board review style question #2
    Which of the following is true about colon cancer?

  1. Commonly mutated genes include APC, TP53 and KRAS
  2. Most cases are poorly differentiated
  3. Most cases are positive for CK7 and negative for CK20 and CDX2
  4. Superficial / early tumors metastasize often
Board review style answer #2
A. Commonly mutated genes include APC, TP53 and KRAS

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Reference: Adenocarcinoma
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