Tyrosine kinase receptor expression in thymomas.
OBJECTIVE
Promising new therapies for neoplasia include tyrosine kinase receptor antagonists. Tyrosine kinase oncogenes present an appealing anti-tumor drug target since they play an integral role in a variety of cellular responses including cell proliferation and differentiation. We previously demonstrated a high rate of epidermal growth factor receptor (EGFR) expression in advanced-stage thymic epithelial tumors. More recently, we have examined c-KIT (CD117) expression in a similar series of tumors.


METHODS
Tumor from 35 patients seen at our institution for treatment of advanced-stage thymoma was available. Twenty thymomas and 15 thymic carcinomas were assessed for c-KIT expression. Tissue sections of tumor were stained immunohistochemically with anti-c-KIT (Oncogene). Either cytoplasmic or membrane staining was considered positive. Appropriate controls were performed. Positive staining for c-KIT was present in 12 tumors (11 thymic carcinomas and 1 thymoma).


RESULTS
In distinction to EGFR, c-KIT is expressed more commonly in thymic carcinomas (73% of carcinomas) than in thymoma (5% of thymomas).


CONCLUSIONS
An EGFR negative/c-KIT positive staining pattern is typical of thymic carcinoma, whereas thymomas are generally EGFR positive/c-KIT negative. Possible therapeutic implications of these observations remain to be determined.
Henley
John D
JD
Department of Pathology, Indiana University School of Medicine, Clarian Health Partners, 550 North University Blvd, Rm 3465, Indianapolis 46202, USA. jhenley@iupui.edu
Cummings
Oscar W
OW
Loehrer
Patrick J
PJ
D002277:Carcinoma / Q000737:chemistry* / Q000556:secondary; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis* / Q000276:immunology; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis*; D013945:Thymoma / Q000737:chemistry* / Q000556:secondary; D013953:Thymus Neoplasms / Q000737:chemistry* / Q000473:pathology
D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases