# Merkel cell polyomavirus (MCPyV) status

Source: https://onco.cc/terms/mcpyv-status/  
OnCo record `mcpyv-status` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

About eight in ten Merkel cell carcinomas are driven by a common skin virus that has stitched itself into the tumour's DNA; the virus-negative rest are driven by sunlight and carry a huge mutation load. Both respond to immunotherapy, and in virus-positive patients a blood antibody test against the viral protein can track the cancer after treatment.

## Summary

What is measured: whether a Merkel cell carcinoma carries integrated Merkel cell polyomavirus, and the patient's antibody response to its oncoproteins. How: immunohistochemistry for the viral large T antigen (CM2B4 antibody) or PCR for viral DNA on the tumour; serum antibodies to the small and large T oncoproteins (the AMERK test) in about half of patients at diagnosis, whose titre falls after successful treatment and rises months before a recurrence is visible (antibodies to the capsid protein are common in healthy people and useless). Virus-negative tumours carry an ultraviolet mutational signature, very high tumour mutational burden and TP53 and RB1 mutations; virus-positive tumours have few mutations yet respond just as well to PD-1 and PD-L1 blockade (avelumab in JAVELIN Merkel 200, pembrolizumab in KEYNOTE-017, retifanlimab). What a result changes: prognosis (virus-positive slightly better), the surveillance strategy (serial titres in seropositive patients in place of some imaging), stratification in trials, and eligibility for T-cell therapies directed at viral antigens. Where it matters: Merkel cell carcinoma.

## Fields

- Kind: Term
- Last checked: 2026-09-17
- Also known as: MCPyV; Merkel cell polyomavirus; MCV; virus-positive Merkel cell carcinoma; virus-negative Merkel cell carcinoma; MCPyV-positive; MCPyV-negative; large T antigen; CM2B4; MCPyV oncoprotein antibodies; AMERK; Merkel polyomavirus antibody titre

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Merkel_cell_polyomavirus
- Wikipedia: https://en.wikipedia.org/wiki/Merkel_cell_polyomavirus

## Connected records

- drugs: [Avelumab](https://onco.cc/drugs/avelumab/), [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [Retifanlimab](https://onco.cc/drugs/retifanlimab/)
- terms: [Immunohistochemistry (IHC)](https://onco.cc/terms/ihc/), [Mutational signature](https://onco.cc/terms/mutational-signature/), [Tumour markers (CEA, LDH, chromogranin, thyroglobulin)](https://onco.cc/terms/tumour-markers/), [Tumour mutational burden (TMB)](https://onco.cc/terms/tmb/)
- cancers: [Merkel cell carcinoma](https://onco.cc/cancers/merkel-cell-carcinoma/)

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