[Hyperplasia of the thyroid gland].
Hyperplasia of the follicular epithelium (goitre) is the most common morphological change in the thyroid seen by the pathologist. The present paper deals with the aetiology, epidemiology and clinical features of thyroid hyperplasia and its differential diagnosis from thyroid adenoma. Neoplastic hyperplasia of the calcitonin-producing thyroid C cells gives rise to familial medullary carcinoma. The second part of the paper deals with the definition of neoplastic C cell hyperplasia and its discrimination from physiological C cell hyperplasia.