2021 Volume 48 Issue 3 Pages 113-120
Purpose: The aim of this study was to investigate the incidence of fine strong echoes in benign and malignant thyroid nodules and their causative substances, as well as whether it was possible to ultrasonographically distinguish them. Subjects and Methods: A total of 144 resected nodules were used, including 56 cases of papillary carcinoma (PC), four cases of follicular carcinoma (FC), 57 cases of follicular adenoma (FA), and 27 cases of adenomatous goiter (AG). We compared and examined ultrasonographic and histologic findings for each histological type, with a particular focus on the features of fine strong echoes, their causative substances, and the correlation between them. Results: Fine strong echoes were observed in PCs with a significantly high incidence of 69.6% (39 cases, p＜0.0001), but also in 21.1% of FA (12 cases) and 25.9% of AG (7 cases). In the 58 positive cases, one or two of five microstructures (psammoma bodies, irregular-shaped microcalcifications in fibrous stroma, calcium oxalate crystal, cholesterol crystals, and psammoma body-like structures) were histologically observed, while they were absent in 76 of the 86 negative cases. Discussion: The presence or absence of fine strong echoes was coincident with the presence or absence of the five microstructures in 93.1% of cases. Fine strong echoes on ultrasound images were considered to reflect these microstructures. Fine strong echoes due to the microstructures looked like each other, but taking incidental findings into account, ultrasonographic estimation of the microstructures may be possible. In anechoic nodules, slow-moving fine strong echoes with comet signs and fixed ones are likely to be cholesterol crystals and calcium oxalate crystals, respectively. Conclusion: Fine strong echoes were observed in 22.6% of benign thyroid nodules. Their causative substances were four types of microstructures other than psammoma bodies. Calcium oxalate crystals and cholesterol crystals in the anechoic nodules may be estimated based on ultrasound images, although it seems difficult to distinguish them in most cases.
