title: Immunohistochemical markers in the differentiation of thymic and pulmonary neoplasms.
abstract: OBJECTIVE
  The histopathological features of some thymic neoplasms overlap with those of pulmonary squamous and large-cell undifferentiated carcinomas, and identification of the primary site may be difficult on routine staining. We have assessed a panel of antibodies that may help to distinguish between neoplasms from these two sites.
  
  
  RESULTS
  Antibodies identifying cytokeratin 7 (CK7), CD5, CD10, CD1a and thyroid transcription factor-1 (TTF-1) were applied to a series of 20 thymic neoplasms (thymic carcinomas, atypical thymomas and thymomas), 10 primary squamous cell carcinomas of the lung and 10 large-cell undifferentiated carcinomas of the lung. Staining for TTF-1 was positive in 3/10 large-cell undifferentiated carcinomas, but negative in all other tumours. CD5 showed strong membranous staining in 3/6 thymic carcinomas and 1/14 thymomas, but only focal staining in 1/20 pulmonary carcinomas. CD1a was consistently positive in thymic lymphocytes in both typical and atypical thymomas, but only focally in 1/6 thymic carcinomas. CD1a stained dendritic cells in 7/20 pulmonary carcinomas, but did not stain lymphocytes. Staining for CK7 and CD10 did not aid in differentiating between a pulmonary or thymic origin of the tumour.
  
  
  CONCLUSIONS
  Staining for TTF-1, CD5 and CD1a have potential use in distinguishing between pulmonary and thymic neoplasms.
authors.affiliation: Department of Histopathology, Royal Brompton Hospital, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Pomplun
authors.forename: A C
authors.initials: AC
authors.lastname: Wotherspoon
authors.forename: G
authors.initials: G
authors.lastname: Shah
authors.forename: P
authors.initials: P
authors.lastname: Goldstraw
authors.forename: G
authors.initials: G
authors.lastname: Ladas
authors.forename: A G
authors.initials: AG
authors.lastname: Nicholson
mesh_terms: D018949:Antigens, CD1 / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D018956:CD5 Antigens / Q000378:metabolism; D018287:Carcinoma, Large Cell / Q000378:metabolism / Q000473:pathology*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology*; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D003937:Diagnosis, Differential; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology*; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D013945:Thymoma / Q000378:metabolism / Q000473:pathology*; D013953:Thymus Neoplasms / Q000378:metabolism / Q000473:pathology*; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D018949:Antigens, CD1; D014408:Biomarkers, Tumor; C419393:CD1a antigen; D018956:CD5 Antigens; C000614412:NKX2-1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors