[Thyroid nodule: benign or malignant?].

A thyroid nodule is a frequent occurrence. Its prevalence in a general adult population is about 50% and can even reach 67% when a cervical echography is performed. Only 5% of these nodules are cancers, and it is therefore important to avoid an useless and riskful surgery. This presentation is based on the Medical Guidelines for Clinical Practice: American Association of Clinical Endocrinologists (AACE), Associazione Medici Endocrinologi (AME) and European Thyroid Association (ETA) in 2010 for the Diagnosis and Management of Thyroid Nodules. In the absence of prospective randomized studies, these recommendations are established on the best evidence level. The patient history and clinical signs give some informations about potential risks. Thyroid tests not only evaluate thyroid functional status but TSH value and the presence of antithyroglobuline antibody seem to be associated with a higher risk of malignancy. A thyroid scintigraphy detects the presence of hot thyroid nodules. The thyroid echography is a key element before fine needle aspiration cytology. Some echographic criteria in the TIRADS (Thyroid Imaging Reporting and Data System), classification can reach an 88% sensitivity, a 49% specificity, a 49% positive predictive value, an 88% negative predictive value and a 94% diagnostic accuracy. The fine needle aspiration cytology performed with echography will be crucial to decide if the patient is to be eligible for surgery. In 70 to 80% of the cases, nodules can be classified as benign or malignant with a 92% negative predictive value for a benign diagnosis and a 100% positive predictive value for a diagnosis of cancer. The discovery of a follicular proliferation (cancer incidence of 20-30%) is a grey zone. Follicular proliferation and definite cancer lead of course to a surgical option. A decisional tree summarizes the different steps leading to a therapeutic decision.