Expression of c-erbB-3 and c-erbB-4 proteins in papillary thyroid carcinomas.

c-erbB-3 and c-erbB-4 protein expression was analyzed using immunohistochemistry in 138 fresh-frozen thyroid tissue samples from 106 patients, including 56 cases of papillary thyroid carcinoma. Increased expression of c-erbB-3 and c-erbB-4 proteins was observed in papillary carcinomas compared to nonneoplastic thyroid tissue. No amplifications of the c-erbB-3 and c-erbB-4 genes were detected. Coexisting overexpression of epidermal growth factor receptor, c-erbB-2, c-erbB-3, and c-erbB-4 was demonstrated in 36 (64%) of 56 papillary thyroid carcinomas. These findings suggest a common regulatory mechanism for the type I (epidermal growth factor receptor-related) receptors in papillary thyroid carcinomas and provide numerous possibilities for functional receptor interactions.