THE IMPACT OF GEOGRAPHICAL, CLINICAL, DIETARY AND RADIATION-INDUCED FEATURES IN EPIDEMIOLOGY OF THYROID-CANCER

Cancer of the thyroid accounts for less than 1% of all cancers recogni sed each year, but the incidence is rising. Much of the early work of the epidemiology and aetiology of thyroid cancer was based on the assu mption that thyroid cancer can be treated as an entity. The recognitio n that two distinct types of endocrine cell occur within the thyroid h as made it clear that any discussion of the aetiology and epidemiology of thyroid malignancies must take into account the histological class ification of these tumours. Moreover, there are difficult problems to be considered when comparing thyroid cancer incidence across tumour re gistries, because of a lack of standardisation of morbidity data colle ction, difficulties in histological diagnosis, varying rates of diagno sis of occult papillary carcinoma, and prevalence and techniques of au topsies. So far only a relatively small proportion of thyroid cancer c ases can be explained with adequate certainty as regards epidemiology and aetiology. As in cancer in general, the aetiology and epidemiology of thyroid cancer in detail remains unknown in the majority of cases.