Box-and-whisker plots representing the COX-2 gene expression by quantitative RT-PCR in NNG, PTC and HT groups (FNAB). Results are calculated as RQ values. Whiskers represent mean ± SD (standard deviation) for particular groups. Boxes represent mean ± SEM (standard error of mean). The results were statistically analyzed using the Kruskal-Wallis test (p < 0.0001).