title: Chronic lymphocytic leukaemia patients have a high risk of Merkel-cell polyomavirus DNA-positive Merkel-cell carcinoma.
abstract: BACKGROUND
  Immunosuppression and Merkel-cell polyomavirus (MCPyV) infection may have a role in the pathogenesis of Merkel-cell carcinoma (MCC), a rare neuroendocrine carcinoma of the skin.
  
  
  METHODS
  We studied incidence of chronic lymphocytic leukaemia (CLL) and MCC from the files of the Finnish Cancer Registry and the largest hospital of Finland, Helsinki University Central Hospital, from 1979 to 2006. Presence of MCPyV DNA in MCCs was investigated by quantitative PCR.
  
  
  RESULTS
  We identified 4164 patients diagnosed with CLL and 172 diagnosed with MCC. Six patients diagnosed with both diseases were found; CLL was the first diagnosis in four cases and MCC in two. The standardised incidence ratio (SIR) for CLL after the diagnosis of MCC was highly elevated, 17.9 (95% confidence interval (CI), 2.2-64.6; P<0.001), and the SIR for MCC after the diagnosis of CLL was also elevated, 15.7 (3.2-46.0, P<0.01). Merkel-cell polyomavirus DNA was present in all five MCCs with tumour tissue available for analysis.
  
  
  CONCLUSIONS
  We conclude that patients diagnosed with CLL have a substantially increased risk for MCC, and vice versa. Merkel-cell polyomavirus DNA is frequently present in MCCs that occur in CLL patients. Immunosuppression related with CLL and viral infection might explain the association between CLL and MCC.
authors.affiliation: Department of Plastic Surgery, Helsinki University Central Hospital, Helsinki, Finland. virve.koljonen@hus.fi
authors.forename: V
authors.initials: V
authors.lastname: Koljonen
authors.forename: H
authors.initials: H
authors.lastname: Kukko
authors.forename: E
authors.initials: E
authors.lastname: Pukkala
authors.forename: R
authors.initials: R
authors.lastname: Sankila
authors.forename: T
authors.initials: T
authors.lastname: Böhling
authors.forename: E
authors.initials: E
authors.lastname: Tukiainen
authors.forename: H
authors.initials: H
authors.lastname: Sihto
authors.forename: H
authors.initials: H
authors.lastname: Joensuu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015266:Carcinoma, Merkel Cell / Q000209:etiology* / Q000821:virology; D004279:DNA, Viral / Q000032:analysis; D005260:Female; D006801:Humans; D007165:Immunosuppression Therapy; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000150:complications*; D008297:Male; D018862:Merkel Cells / Q000821:virology*; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011120:Polyomavirus / Q000302:isolation & purification*
chemical_list: D004279:DNA, Viral