Cytoplasmic staining of erbB-2 but not mRNA levels correlates with differentiation in human thyroid neoplasia

OBJECTIVE Amplification and overexpression of the erbB-2 proto-oncogene in human carcinomas may have prognostic significance. its role in thyroid carc inoma is controversial. We investigated human thyroid tumours for erbB-2 ge ne amplification, activating mutations in the transmembrane domain, quantit ative mRNA expression and protein expression. MATERIALS AND METHODS DNA and mRNA were extracted from 47 morphologically c haracterized, frozen thyroid tumours including 10 nodular hyperplasias, 3 f ollicular carcinomas and 34 papillary carcinomas (4 with tall-cell features , 2 with insular and 2 with anaplastic de-differentiation), DNA amplificati on was analysed by differential PCR, The transmembrane domain of erbB-2 was sequenced in all tumours for activating mutations in position 659, Levels of mRNA expression were determined by competitive mRNA RT-PCR, Immunohistoc hemistry (IHC) for erbB-2 protein expression in corresponding paraffin-embe dded samples was evaluated. RESULTS Our results showed no DNA amplification of erbB-2, Sequencing of th e transmembrane domain of erbB-2 revealed no activating mutations, The leve l of mRNA expression was variable, 11 papillary carcinomas showing statisti cally significant elevated mRNA levels compared with corresponding normal t hyroid tissue; however, this did not correlate with other indicators of poo r prognosis, in contrast to elevated mRNA levels in tumours, the level of p rotein staining correlated with degree of differentiation, normal and hyper plastic tissue being strongly positive and poorly differentiated tumours ne gative. CONCLUSION There are no mutations or amplifications of the erbB-2 gene in h uman thyroid tumours, Elevated erbB-2 mRNA expression in some thyroid tumou rs is not associated with clinical features of poor prognosis; however, the significance of the elevated mRNA levels is unclear, as it did not result in protein overexpression, Instead, cytoplasmic erbB-2 protein detection by IHC correlates with differentiation of human thyroid tumours and may be a feature of good prognosis.