We (Marques et al, 2002) and others (Kroll et al, 2000; Nikiforova et al, 2002; Aldred et al, 2003; Cheung et al, 2003) have detected cases of thyroid tumours, such as FTC, FTA or PTC, that exhibit mild or moderate diffuse PPARγ nuclear staining, even though they are RT–PCR negative for the PAX8-PPARγ fusion gene. This evidence concerns the gene PAX8 and thyroid tumor.