[Echography of thyroid nodules. The echography specialist facing the clinician's requirements].

The risk of malignancy in cases of unique non-functional thyroid nodules ranges from 5 to 20% and since definitive diagnosis can only be provided by the pathology examination, surgical removal could be planned in all cases. The clinician however also has the objective of proposing surgery to as few patients with benign nodules as possible and thus calls upon the echographist to help distinguish between malignant and benign nodules. Thus orders for echography carry an intrinsic request for diagnostic arguments, a precise analysis of the characteristics of the nodule and a description of possible multinodular dystrophy as well as an estimation of the probability of malignancy. The echographist's report must include a precise description of each thyroid lobe, the localization of the nodule, its size, contour, echostructure, echogenicity and calcifications. The cervical lymph node chains must also be explored. An analysis of the surrounding parenchyma can frequently confirm multinodular dystrophy. The size of the nodule is the determining factor in predicting malignancy. While for very small nodules, less than 1 cm in diameter, the malignant nature cannot be reasonably predicted, and inversely for very large nodules, invading an entire lobe, it is usually evident, for intermediate sized nodules, echography is a strategic diagnostic tool. No sign is pathognomonic but an association of arguments can favour malignancy: an unique isolated nodule, irregular contours, lymph node enlargement greater than 1 cm. Hypoechogenicity is another important characteristic with a positive predictive value of 50% to 63%. Overall, the sensitivity of echography is good at 75% with specificity of 61 to 83%.(ABSTRACT TRUNCATED AT 250 WORDS)