['Recent studies strongly suggest the use of oncofetal fibronectin (onfFN) mRNA in diagnostic follow-up and staging due to its very high specificity for thyroid cancers. Since the use of this marker has not been well established yet, particularly in the monitoring of minimal residual disease, we have tried to verify the diagnostic power of onfFN and its usefulness as a prognostic molecular marker. For this reason, we evaluated (by RT-PCR) the presence of onfFN mRNAs, not only in blood samples and thyroid tissues (both normal and neoplastic), but also in different biological fluids (such as K3-EDTA blood samples, saliva and urine) belonging to healthy individuals.', 'Molecular investigations, such as RT-PCR protocol, and sequencing of onfFN cDNAs evaluation of the above-mentioned samples were performed.', 'The onfFN transcript was largely expressed in all benign and malignant thyroid tissues [differentiated thyroid carcinomas (DTCs)] tested as well as in a large number of biological fluids; in particular, 100% urine samples were positive for onfFN transcript as compared to the thyroglobulin (Tg) mRNA (75%), while saliva was always positive for onfFN and never for Tg. These findings indicate that onfFN cannot be considered a marker specific for thyroid cancer presence. Finally, Tg results were positive in a large part of the samples, but not always in concomitance with onfFN.'] Does blood presence of circulating oncofetal fibronectin mRNA , by RT-PCR , represent a useful specific marker for the management and follow-up of thyroid cancer patients?