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invasive colorectal adenocarcinoma

Friday 15 February 2013

Definition: Invasive adenocarcinoma requires invasion through the muscularis mucosae at least into the submucosa

Synopsis

- Varying degrees of gland formation (see Grading at left)

  • Typically lined by tall columnar cells

- Frequent desmoplastic response
- Dirty necrosis commonly seen

  • Extensive central necrosis composed of granular eosinophilic karyorrhectic debris
  • Frequent surrounding garland of cribriform glands

Microsatellite instability and/or hereditary non-polyposis colorectal carcinoma syndrome (HNPCC)

The following features are suggestive of microsatellite instability and/or hereditary non-polyposis colorectal carcinoma syndrome (HNPCC) but may also be seen in a subset of sporadic adenocarcinomas

- Intraepithelial lymphocytes, ≥3 per HPF
- Crohn-like response at edge of carcinoma

  • Lymphoid aggregates / follicles with or without germinal centers not associated with a lymph node

- Mucinous or signet ring carcinoma component
- Medullary carcinoma
- Less specific criteria

  • Right side location
  • High grade histology
  • Lack of dirty necrosis

- Sporadic carcinomas with these features are frequently MSI high

  • Such carcinomas share essentially all histologic features with HNPCC tumors
  • May be present in 15% of colorectal adenocarcinomas
  • Familial and sporadic cases share some other clinical features
    • Better prognosis than non-MSI carcinomas
    • Decreased response to 5-FU therapy
    • Right sided predominance

Circumferential / radial margin

- Circumferential / radial margin applies to rectum and non-peritonealized surfaces of colon

  • It does not apply to peritoneal surface

Prognosis

Following features may have prognostic value but have not been sufficiently validated:

- Tumor border configuration

  • Expansile – smooth and pushing
  • Infiltrative
    • Limit of carcinoma not definable on naked eye exam of slide
    • Inability to resolve carcinoma from host response on naked eye exam of slide
    • Streaming dissection / permeation of muscularis propria without desmoplastic response
    • Dissection of pericolic fat by single cells, cords or clusters of cells
    • Perineural invasion
  • Budding
    • Based on high power examination of edge of carcinoma
    • Detached clusters ≤5 cells each embedded in desmoplastic stroma
    • May become spindled (epithelial-mesenchymal transition)
    • More often seen in MSI carcinomas associated with HNPCC and with MSS carcinomas but not with sporadic MSI carcinomas

Types

Special types of carcinoma are covered separately

- Adenosquamous

  • Both glandular and squamous components are malignant

- Medullary

  • Pushing border, many intraepithelial lymphocytes

- Mucinous

  • >50% composed of mucin

- Poorly differentiated endocrine

  • Both small cell and large cell with endocrine differentiation

- Signet ring

  • >50% signet ring cells

- Squamous
- Undifferentiated

  • 0% gland formation

- Invasive carcinoma involving an adenomatous polyp
- Adenosquamous colorectal carcinoma
- Hereditary non-polyposis colorectal carcinoma
- Medullary colorectal adenocarcinoma
- Mucinous colorectal adenocarcinoma
- Poorly differentiated endocrine carcinoma
- Signet ring colorectal adenocarcinoma
- Squamous colorectal carcinoma
- Undifferentiated colorectal carcinoma

See also

- intramucosal colorectal adenocarcinoma

References

- American Joint Committee on Cancer Prognostic Factors Consensus Conference: Colorectal Working Group. Compton C, Fenoglio-Preiser CM, Pettigrew N, Fielding LP. Cancer. 2000 Apr 1;88(7):1739-57. PMID: 10738234

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