Elastographic patterns of thyroid microcarcinomas: a new proposal

Introduction: Ultrasound (US) elastography for thyroid microcarcinomas has variable diagnostic performance.This study aimed to (1) define the elastographic features of thyroid nodules using two-dimensional shear-wave elastography (2D-SWE) and ( 2) evaluate the utility of combining conventional US, elastography-strain (E-strain), and 2D-SWE for improving diagnostic performance in thyroid micronodules.Materials and Methods: Patients with thyroid nodules were evaluated in a cross-sectional study with conventional US, E-strain, and 2D-SWE.Nodule stiffness, the presence of a perinodular halo, and the halo/nodule A/B index were evaluated using 2D-SWE.Three elastographic patterns were defined based on conventional US, E-strain, and 2D-SWE features.The pathological diagnosis was made by fine needle aspiration biopsy and confirmed by surgery.Results: We included 158 patients with 158 thyroid nodules: 64 micronodules ≤10 mm and 94 macronodules > 10 mm.Malignancy was confirmed in 58 (36.7%) of 158 nodules, of which 29 were thyroid microcarcinomas.Stiffness at a cutoff value of 23.5 kPa predicted malignancy.Notably, 21 (72.4%) of 29 microcarcinomas with a perinodular halo had a stiffness value of < 23.5 kPa.All microcarcinomas with a perinodular halo (n = 21, 100%) had an elastographic stiffness A/B index ≥ 1.3.A congruent elastographic pattern was defined as thyroid imaging reporting and data system (TI-RADS) 4 or 5, E-strain pattern 4 or 5, with a stiffness ≥ 23.5 kPa without a perinodular halo, and an A/B index < 1.3 by 2D-SWE.An incongruent elastographic pattern was defined as TI-RADS 4 or 5, E-strain pattern 4 or 5, and discordant findings on 2D-SWE with intrinsic thyroid nodule laxity (< 23.5 kPa), a rigid perinodular halo, and an A/B index ≥ 1.3.An atypical congruent elastographic pattern was defined as TI-RADS 4 or 5 with atypical findings on E-strain (pattern 1, 2, or 3), and 2D-SWE with intrinsic thyroid nodule laxity (< 23.5 kPa), a rigid perinodular halo, and an A/B index ≥ 1.3.Conclusion: Three elastographic patterns of thyroid microcarcinomas are proposed based on 2D-SWE features such as nodule stiffness, a perinodular halo, and an A/B index in combination with conventional US and E-strain.These elastographic patterns have not been described in the literature.