Primary malignant tumours of the thyroid: the relationship between histological classification and clinical behaviour.

One hundred and seventy-nine primary malignant tumours of the thyroid seen at The London Hospital between 1945 and 1972 were classified by the system of Woolner et al. (1961) and Hazard (1964). The distinct pathological and clinical features of the differentiated primary carcinomas and the similarities and differences between malignant lymphoma and anaplastic carcinoma were confirmed. This study showed the 'benign' behaviour of more than half the 'differentiated' papillary and follicular carcinomas when treated by thyroid lobectomy and the very malignant nature of anaplastic carcinomas and lymphomas whatever their treatment. The behaviour of medullary carcinoma was closer to that of the other differentiated tumours than to the undifferentiated varieties. Our patients were not thought to have been exposed to known goitrogens or previous thyroid irradiation.