Introduction: In differentiated thyroid cancer (DTC) the differentiation between reactive and metastatic lymph nodes is difficult at the early stages of metastasis. The aim of the study was to assess the results of fine needle aspiration (FNA) samples examination by the use of RT-PCR for Tg mRNA. The special attention was directed to the evaluation of specificity of TgRNA estimation.
Material and methods: The group consisted of 193 DTC patients with suspicion of lymph node recurrence and at least one positive RT-PCR result. Thyroglobulin RT-PCR was conducted in residual material left after preparation of cytological smears from FNA specimens. Primer spanning exons 3-5 were used with 39 cycles of PCR. RNA isolation control and cDNA amplification were carried out using GAPDH starters. 308 lymph node biopsies were included.
Results: 246 positive results for Tg RNA were observed in the analyzed group, 71.1% confirmed by FNA. Among other 71 results, in which cytological examination did not correspond unequivocally to molecular findings, in 34 metastases were confirmed both by cytological and clinical examination. There were 11 patients operated due to the positive serial molecular examination only. In 10 (91%) of them DTC metastases were confirmed. So, the positive predictive value of the molecular result ranged between 75-89% and the negative one was 100%.
Conclusions: In DTC patients RT-PCR Tg mRNA is helpful in qualification of suspicious lymph nodes to surgery in DTC patients. At the negative cytological finding, the positive molecular result constitutes an indication for early surgery.