Epidermal growth factor receptor protein expression and gene amplification in small cell carcinoma of the urinary bladder.

PURPOSE: Small cell carcinoma of the urinary bladder is a highly aggressive malignancy with an average life expectancy of only a few months. Epidermal growth factor receptor (EGFR) has been implicated in the pathogenesis and progression of many malignancies. This study was done to investigate EGFR protein expression and gene amplification in a large series of small cell carcinomas of the urinary bladder. EXPERIMENTAL DESIGN: Fifty-two cases of urinary bladder small cell carcinoma were included in this study. Immunostaining for EGFR was done on paraffin-embedded tissue sections, and gene amplification for EGFR was done by fluorescence in situ hybridization. EGFR expression was correlated with clinicopathologic characteristics and clinical outcome. RESULTS: All 52 patients, except 1, had advanced disease (T2 or above) at presentation. Immunohistochemically, positive EGFR expression was observed in 14 of 52 (27%) cases. No EGFR gene amplification was observed in any of 52 cases by fluorescence in situ hybridization. Forty cases had polysomy and the remaining 12 cases displayed disomy. No correlation between EGFR protein expression and gene amplification was shown. There was no correlation between EGFR expression and clinicopathologic characteristics. CONCLUSIONS: EGFR is expressed in a subset of urinary bladder small cell carcinomas; however, expression of EGFR does not correlate with clinicopathologic variables. At the molecular level, EGFR overexpression in small cell carcinoma of the urinary bladder does not seem to be caused by gene amplification. The expression of EGFR raises the possibility that EGFR may be a potential therapeutic target in the treatment of this malignancy.