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 morphological type of
thyroid tumour and its epidemiology, natural history, function,
prognosis and response to therapy has been further strengthened since
the first edition. In par- ticular, the decision taken to separate
papillary and follicular carcino- mas and exclude a mixed papillary
follicular type has been well justi- fied. One of the major changes has
been the recognition that many tu- mours regarded 20 years ago as small
cell carcinoma were really ma- lignant lymphoma, and this development
has been incorporated into this edition, with increased importance given
to primary malignant lymphoma of the thyroid. Much work has also been
done on medul- lary carcinoma of the thyroid, its link with mUltiple
endocrine neo- plasia syndromes, and its association in its inherited
form with C-cell hyperplasia; this too is recognized by an expanded
section on this tu- mour.