The majority of follicular tumours (more than 90%) are well-differentiated, usually retain in varying degrees biological properties of normal follicular cells (i.e. iodine uptake; thyroglobulin synthesis), and are mainly divided into papillary (PTC) and follicular (FTC) carcinomas on the basis of the histological features (Rosai et al. 1992; Schlumberger, 2007). The gene discussed is TG; the disease is carcinoma.