title: Merkel cell carcinoma can be distinguished from metastatic small cell carcinoma using antibodies to cytokeratin 20 and thyroid transcription factor 1.
abstract: OBJECTIVE
  To investigate whether immunohistochemical staining for cytokeratin 20 (CK20) and thyroid transcription factor 1 (TTF-1) is useful in distinguishing Merkel cell carcinomas (MCCs) from metastatic small cell carcinomas (SCCs).
  
  
  METHODS
  Eleven cases of MCC and 10 of lung SCC were stained for CK20 and TTF-1.
  
  
  RESULTS
  Ten of 11 MCCs stained with the antibody to CK20. None was positive for TTF-1. No SCC stained with anti-CK20 and all stained strongly with anti-TTF-1.
  
  
  CONCLUSIONS
  The use of both anti-CK20 and anti-TTF-1 can reliably distinguish between MCC and metastatic SCC, thus avoiding the need for a detailed clinical investigation of patients with MCC in whom metastatic SCC must be excluded.
authors.affiliation: Department of Dermatology, Dryburn Hospital, North Road, Durham DH1 5TW, UK.
authors.forename: S N
authors.initials: SN
authors.lastname: Leech
authors.forename: A J
authors.initials: AJ
authors.lastname: Kolar
authors.forename: P D
authors.initials: PD
authors.lastname: Barrett
authors.forename: S A
authors.initials: SA
authors.lastname: Sinclair
authors.forename: N
authors.initials: N
authors.lastname: Leonard
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism*; D015266:Carcinoma, Merkel Cell / Q000175:diagnosis* / Q000378:metabolism; D018288:Carcinoma, Small Cell / Q000175:diagnosis* / Q000378:metabolism / Q000556:secondary*; D003937:Diagnosis, Differential; D006801:Humans; D007124:Immunoenzyme Techniques; D007381:Intermediate Filament Proteins / Q000378:metabolism; D053554:Keratin-20; D008175:Lung Neoplasms / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D007381:Intermediate Filament Proteins; C507499:KRT20 protein, human; D053554:Keratin-20; C000614412:NKX2-1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors