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colorectal medullary carcinoma

Wednesday 24 August 2016

undifferentiated carcinoma, solid type poorly differentiated carcinoma, large cell minimally differentiated carcinoma

PO

Definition: WHO recognized subtype of colon carcinoma with solid growth pattern (Hum Pathol 1999;30:843).

It is relatively rare; usually quoted as @<@ 1% of colorectal neoplasms (Int J Oncol 2010;37:901). Often elderly women (average age 70 years). Usually right sided.

Strongly associated with high degree of microsatellite instability (MSI), indicative of loss of normal mismatch DNA repair (MMR) 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

IHC

Immunohistochemical studies suggest a loss of intestinal differentiation, exemplified by a high percentage of CDX2 negativity.

Medullary carcinoma of the colon retains a significant degree of intestinal differentiation as evidenced by its high percentage of staining for MUC-1, MUC-2, and TFF-3.

Calretinin, MLH-1, and CDX2 may help to differentiate medullary carcinoma from poorly differentiated colonic carcinoma of the colon.

Differential diagnosis

- poorly differentiated colonic carcinoma

  • Undifferentiated or medullary carcinoma is characterized by its distinct histologic appearance and relatively better prognosis compared to poorly differentiated colonic carcinoma.
  • These 2 entities may be difficult to differentiate by light microscopy alone.
  • Immunohistochemical studies suggest a loss of intestinal differentiation, exemplified by a high percentage of CDX2 negativity.

Open references

- Differentiating the undifferentiated: immunohistochemical profile of medullary carcinoma of the colon with an emphasis on intestinal differentiation. Winn B, Tavares R, Fanion J, Noble L, Gao J, Sabo E, Resnick MB. Hum Pathol. 2009 Mar;40(3):398-404. doi : 10.1016/j.humpath.2008.08.014
PMID: 18992917 (Free)

- Poorly differentiated medullary carcinoma of the colon with an unusual phenotypic profile mimicking high grade large cell lymphoma - a unique case report and review of the literature. Nguyen J, Coppola D, Shan Y, Zhang L.
Int J Clin Exp Pathol. 2014 Jan 15;7(2):828-34.
PMID: 24551312 (Free)