colorectal medullary carcinoma

Medullary carcinoma is extremely rare, constituting approximately 5-8 cases for every 10,000 colorectal cancers diagnosed, with a mean annual incidence of 3.47 (±0.75) per 10 million population.

This tumor is characterized by sheets of epithelioid neoplastic cells with large vesicular nuclei, prominent nucleoli, and abundant cytoplasm. It typically has a pushing border on resection specimens, and is characteristically associated with marked tumorinfiltrating lymphocytes.

Medullary carcinoma is a distinctive histologic subtype that is strongly associated with MSI-H.

It usually has a favorable prognosis despite its poorly differentiated or undifferentiated histology.

References

 http://www.thejgo.org/article/view/410/821