Cancers de la thyroïde

Abstract

Thyroid carcinomas are rare and represent 1% of malignant tumours. Women are more likely to have thyroid cancer, at a ratio of three to one. Thyroid cancer may occur in any age group, although it is most common after the age of 30, and its aggressiveness increases significantly in older patients. Most patients present with a thyroid nodule. Thyroid nodules are frequent but only 5% of them are malignant. Over the last two decades, the widespread of diagnostic tools (ultrasonography, cytology) and changes in the surgical and pathological management of thyroid diseases have led to the increase of thyroid cancer, especially papillary microcarcinomas. Thyroid cancer is more frequent in people who have a history of thyroid exposure to radiation during childhood. The diagnosis is based on the histopathological examination that remains difficult in some cases. The most frequent thyroid cancers (papillary and follicular) are cured in 80-90 % of the cases if treated appropriately. Anaplastic cancer is rare and has a very poor prognosis. The primary therapy for thyroid cancer is total or near total thyroidectomy. Lymph node dissection is not systematically undertaken. Radioiodine treatment is advised for high risk patients and needs high levels of TSH to be effective. Then, patients must remain on thyroid hormone therapy for the rest of their lives. Prognosis factors are well defined and prognosis is good in case of differentiated thyroid cancer. Distant metastases are observed in 10% of the patients, and lung and bones are the most common sites. Locoregional recurrences are observed in 7% of the cases. Prolonged follow-up is recommended, based on physical examination, serum thyroglobulin assessment with TSH stimulation (L-thyroxin off or use of human recombinant TSH), ultrasonography and post therapeutic whole body scan.