Knowledge of tumours of the thyroid gland has advanced consider- ably in the 22 years that have elapsed since work was started on the first edition of Histological Typing of Thyroid Tumours. In the intro- duction to that volume it was recognized that the definitions and clas- sifications put forward would need revision in time, and the present text differs substantially from the first edition. As far as is possible, however, the framework of the classification proposed remains the same, as the original classification was widely accepted and proved useful in many studies. The link between the...