Immunohistochemical markers in the differentiation of thymic and pulmonary neoplasms

Histopathology. 2002 Feb;40(2):152-8. doi: 10.1046/j.1365-2559.2002.01328.x.


Aims: 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.

Methods and 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.

Conclusion: Staining for TTF-1, CD5 and CD1a have potential use in distinguishing between pulmonary and thymic neoplasms.

MeSH terms

  • Antigens, CD1 / metabolism
  • Biomarkers, Tumor / metabolism
  • CD5 Antigens / metabolism
  • Carcinoma, Large Cell / metabolism
  • Carcinoma, Large Cell / pathology*
  • Carcinoma, Squamous Cell / metabolism
  • Carcinoma, Squamous Cell / pathology*
  • Cell Nucleus / metabolism
  • Cell Nucleus / pathology
  • Diagnosis, Differential
  • Humans
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology*
  • Neoplasm Proteins / metabolism
  • Nuclear Proteins / metabolism
  • Thymoma / metabolism
  • Thymoma / pathology*
  • Thymus Neoplasms / metabolism
  • Thymus Neoplasms / pathology*
  • Thyroid Nuclear Factor 1
  • Transcription Factors / metabolism


  • Antigens, CD1
  • Biomarkers, Tumor
  • CD1a antigen
  • CD5 Antigens
  • NKX2-1 protein, human
  • Neoplasm Proteins
  • Nuclear Proteins
  • Thyroid Nuclear Factor 1
  • Transcription Factors