Complex and Differential Cytokeratin Profiles in Thymomas and Correlation with Normal Thymus

  • Kerstin Grommisch
  • Walter J. Hofmann
  • Herwart F. Otto
  • Kirsten Willgeroth
  • Roland Moll


Cytokeratins (CKs) are characterized by highly diverse expression patterns and thus serve as potent epithelial differentiation markers. We have studied 31 cases of thymomas (12 cortical, 2 predominantly cortical, 5 mixed, and 9 medullary type thymomas as well as 3 well-differentiated thymic carcinomas) and, for comparison, 15 normal thymi, for the presence of different CK polypeptides. Immunohistochemistry was performed on cryostat sections using the indirect immunoperoxidase method.

In normal medullary epithelial cells, all 16 CKs studied were detected with variable frequencies. Cortical epithelial cells showed less complex patterns, mainly composed of the simple-epithelial CKs 8 and 19 and the stratified-epithelial CK 14. In the subcapsular epithelium, CKs 5, 14 and 19 were predominant.

Analyses of the thymomas revealed a broad spectrum of variably complex CK patterns which, although being fluid, allowed the definition of several quite distinct CK phenotypes. All thymomas co-expressed simple-epithelial (CKs 8, 18, 19) and stratified-epithelial (mainly CKs 5, 14, 15 and 17) CKs. Half of the cortical thymomas revealed a phenotype with predominance of CKs 5 and 15 while 5/9 medullary thymomas showed prevalence of CK 14. Focal expression of CK 6 was more typical of cortical thymomas. CKs 4, 7, 10, 13 and 20 were inconstantly and sparsely expressed, with enhancement of CKs 4, 7 and 13 in cystic structures. “Medullary differentiation” usually was accompanied by a shift towards enhanced stratified-epithelial CKs. Seven cases contained neurofilaments.

The data demonstrate partial correlations between particular CK patterns and the morphological subtypes of thymomas although there are no simple relations to the normal thymic zones. The possible biological significance of the different CK phenotypes needs to be substantiated with larger series.


Thymic Carcinoma Thymic Epithelial Cell Thymic Epithelial Tumor Cytokeratin Expression Normal Thymus 
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Copyright information

© Springer Science+Business Media New York 1997

Authors and Affiliations

  • Kerstin Grommisch
    • 1
  • Walter J. Hofmann
    • 2
  • Herwart F. Otto
    • 2
  • Kirsten Willgeroth
    • 3
  • Roland Moll
    • 3
  1. 1.Institute of PathologyUniversity of MainzMainzGermany
  2. 2.Institute of PathologyUniversity of HeidelbergHeidelbergGermany
  3. 3.Institute of PathologyUniversity of Halle-WittenbergHalle (Saale)Germany

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