Stains & molecular markers
MCPyV (CM2B4)

Resident / Fellow Advisory Board: David B. Chapel, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Thai Yen Ly, M.D.
Noreen M. Walsh, M.D.

Minor changes: 20 April 2021

Copyright: 2020-2021, PathologyOutlines.com, Inc.

PubMed Search: MCPyV[TIAB] OR CM2B4[TIAB] stain

Thai Yen Ly, M.D.
Noreen M. Walsh, M.D.
Page views in 2020: 43
Page views in 2021 to date: 77
Cite this page: Ly TY, Walsh NM. MCPyV (CM2B4). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainsMCPyV.html. Accessed May 6th, 2021.
Definition / general
  • CM2B4 is a monoclonal antibody that detects Merkel cell polyomavirus (MCPyV) large T antigen expression in Merkel cell carcinoma (MCC)
Essential features
Pathophysiology
Interpretation
Uses by pathologists
Prognostic factors
Microscopic (histologic) images

Contributed by Thai Yen Ly, M.D.
MCPyV positive MCC (pure MCC, primary tumor) MCPyV positive MCC (pure MCC, primary tumor)

MCPyV positive MCC (pure MCC, primary tumor)

MCPyV positive MCC (pure MCC, lymph node metastasis) MCPyV positive MCC (pure MCC, lymph node metastasis)

MCPyV positive MCC (pure MCC, lymph node metastasis)


MCPyV negative MCC (combined MCC, primary tumor) MCPyV negative MCC (combined MCC, primary tumor) MCPyV negative MCC (combined MCC, primary tumor) MCPyV negative MCC (combined MCC, primary tumor)

MCPyV negative MCC (combined MCC, primary tumor)

Cytology images

Contributed by Thai Yen Ly, M.D.
MCPyV positive MCC (pure MCC, lymph node metastasis, cytologic preparation of FNA) MCPyV positive MCC (pure MCC, lymph node metastasis, cytologic preparation of FNA)

MCPyV positive MCC (pure MCC, lymph node metastasis, cytologic preparation of FNA)

Positive staining - normal
Positive staining - disease
Negative staining
Molecular / cytogenetics description
  • Genetic profiles for MCPyV positive and MCPyV negative MCCs are distinct
  • MCPyV negative MCCs harbor TP53 and RB1 gene mutations, UV signature mutations and overall higher mutational burden (Oncotarget 2016;7:3403, Cancer Res 2015;75:5228)
Board review style question #1

Which of the following describes the oncogenic virus causally associated with the majority of Merkel cell carcinomas (shown above)?

  1. Herpesvirus with presence corresponding to cytoplasmic IHC expression
  2. Herpesvirus with presence corresponding to nuclear IHC expression
  3. Papillomavirus with presence corresponding to membranous IHC expression
  4. Papillomavirus with presence corresponding to nuclear IHC expression
  5. Polyomavirus with presence corresponding to dot-like paranuclear IHC expression
  6. Polyomavirus with presence corresponding to nuclear IHC expression
Board review style answer #1
F. Merkel cell polyomavirus (MCPyV) is a novel human polyomavirus causally associated with the majority of Merkel cell carcinomas (MCC) (up to ~80%). A nuclear pattern of CM2B4 immunoreactivity in MCC indicates MCPyV large T antigen expression (virus positivity).

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Reference: MCPyV (CM2B4)
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