For thyroid tumours, it has been shown that anaplastic tumours have higher Ki67 indices than well-differentiated thyroid tumours (Carr et al, 1993), and that Hürthle cell carcinomas of the thyroid have higher Ki67 indices than benign Hürthle cell adenomas (Erickson et al, 2000). The gene discussed is MKI67; the disease is Thyroid Gland Oncocytic Follicular Carcinoma.