Merkel cell polyomavirus (MCPyV) in chronic lymphocytic leukemia/small lymphocytic lymphoma

Merkel cell polyomavirus (MCPyV) is a novel polyomavirus that shows a strong association with Merkel cell carcinoma (MCC). Recent studies have demonstrated MCPyV in some cases of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), a malignancy with a similar demographic as MCC. We tested for the presence of MCPyV by PCR and immunohistochemistry in 18 cases of CLL/SLL. Very low-level MCPyV DNA was detected in 33% of CLL/SLL cases by real-time PCR, but only one case demonstrated immunohistochemical positivity for MCPyV. MCPyV was not identified in 17 cases of follicular lymphoma, suggesting either that MCPyV is involved in CLL/SLL pathogenesis or that the immunodeficiency state of CLL/SLL induces low-level MCPyV reactivation.