Topic Completed: 1 November 2015

Minor changes: 1 October 2020

Copyright: 2002-2020,, Inc.

PubMed Search: Medullary carcinoma [title] colon

Raul S. Gonzalez, M.D.
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Cite this page: Gonzalez R. Medullary. website. Accessed December 5th, 2020.
Definition / general
Essential features
  • Strongly associated with high degree of microsatellite instability (MSI), indicative of loss of normal DNA repair gene function
  • Often better clinical outcome independent of stage than microsatellite stable tumors or tumors with low levels of microsatellite instability
  • Usually no / few nodal metastases
  • Older names: undifferentiated carcinoma, solid type poorly differentiated carcinoma, large cell minimally differentiated carcinoma
  • Often elderly women (average age ~70 years)
  • Usually right sided
Case reports
  • Surgery and chemotherapy (although 5-FU not effective, as with other MSI high tumors)
Gross description
  • Large, ulcerating colon mass
Gross images

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Fleshy, ulcerated lesion

Microscopic (histologic) description
  • Malignant, well circumscribed neoplasm with solid growth pattern (no gland formation) and pushing border
  • Can form nested, organoid or trabecular patterns
  • Cells are uniform, polygonal to round, and medium sized with amphophilic cytoplasm, vesicular nuclei with prominent nucleoli and frequent mitotic activity
  • Mucin production absent or very focal
  • Prominent lymphocytic infiltration within and around tumor
Microscopic (histologic) images

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Solid growth pattern

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Medullary (A)

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MLH1-, CDX2-

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Positive stains
Negative stains
Molecular / cytogenetics description
Differential diagnosis
Additional references
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