FNAs are representative of the entire tumor. (a)Dendrogram representing similarities in the gene expression profiles between different FNAs and surgical specimens. FNA-surgical specimen and FNA-FNA pairs from the same patient clustered together more than with samples from any other patient. *Surgical specimen. (b)Representative scatter plots indicating levels of similarity between the cDNA microarray results comparing different specimens. (panels a and b) Comparison of log expression ratios derived from two pretreatment FNAs from the same patient. (panels c and d) Comparison of log expression ratios derived from surgical specimens and the corresponding FNAs from two different patients. (panels e and f) Comparison of log expression ratios derived from two pretreatment FNAs and from a pretreatment FNA and a surgical specimen from different patients, respectively. The correlation coefficient of each comparison is shown at the top left of each panel.