Thyroid carcinomas arise from follicular cells (papillary, follicular, Hurthle, anaplastic), parafollicular cells (medullary) and stroma (lymphoma, sarcoma). Gradation and prognostic factors are different for every one of histological type. Most patients with papillary and follicular thyroid cancer have an excellent prognosis. At the other extreme is anaplastic thyroid cancer whose usual mean survival can be measured in months. Exposure to external radiation and living in endemic goiter area increase the frequency of thyroid cancer. Medullary thyroid carcinoma is often familial and may occur in associations with the multiple endocrine neoplasia syndromes.