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Mucinous Adenocarcinoma of the Colon and Rectum

Definition

  • Adenocarcinoma, arising in the colon or rectum, of which >50% of the lesion is composed of mucin

Return to Colorectal Adenocarcinoma NOS

Diagnostic Criteria

  • Colorectal adenocarcinoma of which >50% of the lesion is extracellular mucin
    • Pools of mucin dissect through the stroma
  • Mucin pools contain malignant epithelium
    • Strips of cells may float freely in or partially line the pools
  • Gland formation and single cells may be seen
  • If <50% of lesion is composed of mucin, designate as:
    • Adenocarcinoma with mucinous component

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates : 1/31/10, 11/12/11

Supplemental studies

Immunohistology

Results for colorectal adenocarcinoma NOS
p63 Negative
CK5/6 5%
CDX2 75-98%
CK7 5-10%
CK20 95

  • CDX2 has been reported to be positive in 70% of colorectal mucinous carcinomas

Differential Diagnosis

Benign Extravasation of Mucin Colorectal Mucinous Adenocarcinoma
Usually associated with a benign lesion Usually has at least areas of usual adenocarcinoma
Usually very few epithelial cells in the pools Usually areas with increased cellularity within the pools
Epithelium usually limited to the point of rupture Usually epithelium is too widespread to be explained by rupture
Epithelial cells present do not show clear evidence of malignancy Epithelial cells may show marked cytologic atypia or cribriform architecture
Usually focal and superficial Usually aggressively dissecting into bowel wall
Frequently associated with inflammation and hemorrhage Usually no inflammation or hemorrhage
The presence of a mucin pool at the base of a GI epithelial neoplasm should prompt a careful examination for mucinous carcinoma

Clinical

  • Poor prognosis
    • Presents at higher stage than usual adenocarcinoma
    • Probably not worse than usual adenocarcinoma when corrected for stage
    • MSI-H carcinomas behave as low grade
  • Spreads preferentially to the peritoneal surface and the ovaries
  • Adenocarcinoma with mucinous component (<50%) has the same pattern of spread

Grading / Staging

Grading

  • Mucinous adenocarcinoma is no longer considered definitionally high grade
    • MSI-H carcinomas are low grade
    • MSS or MSI-L carcinomas are high grade

Staging

Bibliography

  • Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010
  • Sasaki S, Masaki T, Umetani N, Futakawa N, Ando H, Muto T. Characteristics in primary signet-ring cell carcinoma of the colorectum, from clinicopathological observations. Jpn J Clin Oncol. 1998 Mar;28(3):202-6.
  • Kang H, O'Connell JB, Maggard MA, Sack J, Ko CY. A 10-year outcomes evaluation of mucinous and signet-ring cell carcinoma of the colon and rectum. Dis Colon Rectum. 2005 Jun;48(6):1161-8.
  • Pande R, Sunga A, Levea C, Wilding GE, Bshara W, Reid M, Fakih MG. Significance of signet-ring cells in patients with colorectal cancer. Dis Colon Rectum. 2008 Jan;51(1):50-5.

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