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CK20- Merkel cell carcinoma

Sunday 10 April 2016

Merkel cell carcinoma is a rare but highly aggressive cutaneous neuroendocrine carcinoma. Cytokeratin 20 (CK20) is expressed in 95% of Merkel cell carcinomas and is useful for distinction from morphologically similar entities including metastatic small-cell lung carcinoma.

Lack of CK20 expression may make diagnosis of Merkel cell carcinoma more challenging, and has unknown biological significance. Approximately 80% of CK20-positive Merkel cell carcinomas are associated with the oncogenic Merkel cell polyomavirus.

Merkel cell carcinomas lacking Merkel cell polyomavirus display distinct genetic changes from Merkel cell polyomavirus-positive Merkel cell carcinoma, including RB1 inactivating mutations.

Unlike CK20-positive Merkel cell carcinoma, the majority of CK20-negative Merkel cell carcinomas are Merkel cell polyomavirus-negative, suggesting CK20-negative Merkel cell carcinomas predominantly arise through virus-independent pathway(s) and may harbor additional genetic differences from conventional Merkel cell carcinoma.

CK20-negative Merkel cell carcinoma display overlapping genetic changes with CK20-positive Merkel cell carcinoma, including RB1 mutations restricted to Merkel cell polyomavirus-negative tumors. However, some CK20-negative Merkel cell carcinomas harbor mutations not previously described in Merkel cell carcinoma.

Open references

- Next generation sequencing of Cytokeratin 20-negative Merkel cell carcinoma reveals ultraviolet-signature mutations and recurrent TP53 and RB1 inactivation.
Harms PW, Collie AM, Hovelson DH, Cani AK, Verhaegen ME, Patel RM, Fullen DR, Omata K, Dlugosz AA, Tomlins SA, Billings SD. Mod Pathol. 2016 Mar;29(3):240-8. doi : 10.1038/modpathol.2015.154 PMID: 26743471 (Free)

- The Distinctive Mutational Spectra of Polyomavirus-Negative Merkel Cell Carcinoma.
Harms PW, Vats P, Verhaegen ME, Robinson DR, Wu YM, Dhanasekaran SM, Palanisamy N, Siddiqui J, Cao X, Su F, Wang R, Xiao H, Kunju LP, Mehra R, Tomlins SA, Fullen DR, Bichakjian CK, Johnson TM, Dlugosz AA, Chinnaiyan AM. Cancer Res. 2015 Sep 15;75(18):3720-7. doi : 10.1158/0008-5472.CAN-15-0702 PMID: 26238782