Epidermal growth factor receptor expression in invasive thymoma.
OBJECTIVE
Epidermal growth factor receptor (EGFR) is a transmembrane glycoprotein with intrinsic tyrosine kinase activity. Activation results in a variety of cellular responses including cell proliferation and differentiation. In clinical trials, anti-EGFR is showing promise in the treatment of solid tumors expressing EGFR. Thus, we assessed EGFR expression in a series of thymic epithelial tumors.


METHODS
Tumors from 37 patients seen at Indiana University School of Medicine (IUMC) for treatment of thymoma (31 patients) or thymic carcinoma (six patients) were assessed for EGFR expression. Five-micron sections of formalin-fixed, paraffin-embedded tumor (28 invasive and/or metastatic thymomas, six thymic carcinomas, and three non-invasive thymomas) were stained with anti-EGFR. Any degree of cytoplasmic membrane staining of tumor cells was considered positive; furthermore, staining was scored 0 to 3+ using criteria as standardized for HER-2/neu assessment of breast carcinoma. Appropriate controls were performed.


RESULTS
Positive staining of tumor was observed in 28 tumors (23 invasive and/or metastatic thymomas, two thymic carcinomas, and three non-invasive thymomas).


CONCLUSIONS
EGFR is expressed in a high percentage of thymic epithelial tumors. EGFR is often strongly expressed and is a potential therapeutic target in patients with malignant thymic tumors. We are pursuing additional studies to assess anti-EGRF in the treatment of patients with advanced thymoma.
Henley
J D
JD
Department of Pathology, Indiana University School of Medicine, Clarian Health Partners, 550 North University Blvd., Rm 3465, Indianapolis, IN 46202, USA. jhenley@iupui.edu
Koukoulis
G K
GK
Loehrer
P J
PJ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D066246:ErbB Receptors / Q000096:biosynthesis*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018773:Genes, erbB-1 / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D013945:Thymoma / Q000235:genetics* / Q000473:pathology; D013953:Thymus Neoplasms / Q000235:genetics* / Q000473:pathology
D066246:ErbB Receptors