Core I gene is overexpressed in Hürthle and non-Hürthle cell microfollicular adenomas and follicular carcinomas of the thyroid

Most of the steps involved in the initiation and progression of Hürthle (oncocytic, oxyphilic) cell carcinomas of the thyroid remain unknown. Using differential display and semiquantitative RT-PCR we found, among other alterations, overexpression of the gene encoding the Core I subunit of the complex III of the mitochondrial respiratory chain in a follicular carcinoma composed of Hürthle cells. Similar high levels of Core I gene expression were detected in nine follicular carcinomas (seven with Hürthle cell features), in seven microfollicular adenomas (one with Hürthle cell features) and in one micro/macrofollicular adenoma, in contrast to a lower/normal expression in nine papillary carcinomas (three with Hürthle cell features) and five macrofollicular adenomas (one of which displaying Hürthle cell features). No significative correlation was found between Core I overexpression and the proliferative activity of the lesions. We conclude that Core I overexpression in thyroid tumours is not associated with malignancy, Hürthle cells or proliferative activity. The pathogenetic mechanism linking Core I overexpression to the microfollicular pattern of growth of thyroid tumours remains to be clarified