Summary of meta-analyses of studies considering lesion size cut-off thresholds for the assessment of eligibility for FNAB and sonoelastography and inter- and intra-observer agreement in estimating the malignant potential of focal lesions of the thyroid gland

Thyroid cancer is a tumour with a steadily increasing incidence. It accounts for 7% to 15% of focal lesions detected by ultrasound, depending on age, gender and other factors affecting its occurrence. Fine-needle aspiration biopsy is an essential method to establish the diagnosis but, in view of its limitations, sonoelastography is seen as a non-invasive technique useful in differentiating the nature of lesions and monitoring them after fine-needle aspiration biopsy. This paper presents a literature review on the role of both sonoelastographic techniques (relative strain sonoelastography, shear wave sonoelastography) to assess the deformability of focal thyroid lesions. Ultrasound examination is a relatively subjective method of thyroid imaging, depending on the skills of the examiner, the experience of the centre, and the quality of equipment used. As a consequence, there are inconsistencies between the results obtained by different examiners (inter-observer variability) and by the same examiner (intra-observer variability). In this paper, the authors present a review of the literature on inter-observer and intra-observer variability in the assessment of individual features of ultrasound imaging of focal lesions in the thyroid. In addition, the authors report on an analysis of cut-off thresholds for the size of lesions constituting the basis for fine-needle aspiration biopsy eligibility assessment. The need to diagnose carcinomas up to 10 mm in diameter is highlighted, however a more liberal approach is recommended in terms of indications for biopsy in lesions associated with a low risk of malignancy, where, based on consultations with patients, active ultrasound surveillance might even be considered.