Medullary colorectal carcinoma

Medullary colorectal carcinoma is a rare type of colorectal carcinoma.

General

• Rare subtype of colorectal carcinoma.
• Typically has Microsatellite instability.
• Prognostic significance dependent on study.
  • A small series suggests the prognosis of medullary carcinoma with MSI is worse that conventional colorectal carcinoma without MSI.
  • A series with 102 cases suggests a better prognosis when compared on the basis of other pathological characteristics.

Gross

• Well-circumscribed.

Microscopic

Features:

• Poorly differentiated carcinoma:
  • Noninfiltrative border.
  • Solid pattern/nests.
  • No gland formation.
  • Lymphocytic infiltrate.

DDx:

• Other (poorly differentiated) colorectal carcinomas.
• Carcinomas with neuroendocrine differentiation.

IHC

Features:

• CDX2 +ve.
• Beta-catenin +ve.
• MLH1 loss of staining.
• Calretinin (67%-73%)"Differentiating the undifferentiated: immunohistochemical profile of medullary carcinoma of the colon with an emphasis on intestinal differentiation". Hum. Pathol. 40 (3): 398–404. March 2009. doi:10.1016/j.humpath.2008.08.014. PMC 2657293. PMID 18992917. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2657293/."Cadherin-17 and SATB2 are sensitive and specific immunomarkers for medullary carcinoma of the large intestine". Arch. Pathol. Lab. Med. 138 (8): 1015–26. August 2014. doi:10.5858/arpa.2013-0452-OA. PMID 24437456.

Note:

• CDX2, beta-catenin, MLH1 useful for differentiating from poorly differentiated colorectal carcinoma.

See also

• Colorectal adenocarcinoma.