The endocrine incidentaloma
Small, non-palpable thyroid nodules, detectable by thyroid ultrasound (US) in 3050% of the general population, are likely to cause no significant health problem, thus deserving the definition of thyroid incidentalomas. Although clinically overt thyroid cancer is relatively rare, the most relevant issue for thyroid incidentalomas is the exclusion of malignancy by cytological examination of material obtained by fine needle aspiration (FNA). However, in about 30% of samples FNA cytology does not give conclusive results, being non-diagnostic or indeterminate, i.e. unable to discriminate between benign follicular adenoma and thyroid carcinoma. Genetic alterations, such as BRAF mutations or RET/PTC rearrangements, can be detected in FNA material, but for the low specificity and sensitivity, this molecular analysis is not recommended as a routine procedure (ATA GL).
US features associated with malignancy are microcalcifications, hypoechogenicity, irregular margins or absent halo sign, solid pattern, intranodular vascularization and shape (taller rather than wide). However these patterns taken singularly do not have a sufficient predictive value. When combined in the same nodule have a high specificity, but the sensitivity becomes unacceptably low.
US elastosonography (USE) is a new powerful diagnostic technique that assesses hardness as indicator of malignancy. USE performed on selected series of patients has displayed a sensitivity of 97% and a specificity of 100%. The predictivity of USE was independent from the nodule size, being optimal also in nodules <1 cm. Conventional US maintains a pivotal importance to define which nodules are suitable for USE. USE seems to have a great potential as a new tool for the diagnosis of thyroid cancer, especially in small nodules with indeterminate or non diagnostic cytology.