Ultrasonographic risk factors of malignancy in thyroid nodules.

INTRODUCTION: Between 40 and 50 % of the population will have at least one thyroid nodule, although only 5-8 % will have a malignant one.

OBJECTIVE: The objective of this study was to establish the ultrasonographic characteristics which allow us to distinguish benignity from malignancy in thyroid nodules.

METHODS: In the study population, inclusion criteria are (1) a single thyroid nodule and (2) multinodular goiter and exclusion criteria are (1) previous thyroid surgery and (2) fine needle aspiration (FNA) in the past month. This study is a double-blind prospective study. The study protocol is as follows: (1) clinical study; (2) ultrasound examination; (3) FNA; and (4) surgery-follow-up. The variables analysed are as follows: a multinodular nodule or goitre; colloid degeneration; morphology; margins; hyperechoic rim; rim thickness; rim morphology; size; angle between the major axis and the skin; echostructure; posterior acoustic findings; calcifications; thick colloid; localization of the intrathyroid nodular tissue; and characteristics in the Doppler scan.

RESULTS: A total of 221 thyroid nodules were analysed. The following ultrasound findings were associated with malignancy (p < 0.05): a nodule with posterior acoustic shadowing; the echotexture of the nodule; intranodular colloid degeneration; nodule margins; nodular morphology; the presence of thick colloid; the angle between the major axis and the skin; characteristics of the intranodular vessels using color Doppler and Doppler energy; and calcifications. In the multivariate analysis, the following factors persisted as predictors of malignancy: the echotexture of the nodule (odds ratio 12.81), microcalcifications (OR 9.05), and chaotic vascularisation in the Doppler energy (OR 43.47).

CONCLUSIONS: The high-resolution ultrasound allowed for a more reliable diagnosis of malignancy. The main findings of malignancy were the hypoechogenicity echotexture, microcalcifications, and chaotic intranodular vessels using Doppler energy.