Krzysztof Kaliszewski, Dorota Diakowska, Beata Wojtczak, Zdzisław Forkasiewicz

The risk of malignancy from "atypia of undetermined significance/follicular lesion of undetermined significance" (AUS/FLUS) is estimated to lie between 5% and 15%; however, some authors suggest that the risk of malignancy in AUS/FLUS depends upon specific clinical situations. This was a retrospective study which aimed to determine the incidence and risk of thyroid cancer (TC) based upon selected ultrasound features from patients with thyroid nodules (TN) classified as AUS/FLUS. Univariate and multivariate logistic regression analyses were used to identify significant associations between ultrasound features and the risk of TC. Of 127 patients with TN classified as AUS/FLUS who underwent thyroidectomy, 114 (89.8%) had benign disease while 13 (10.2%) had TC. Univariate analysis identified several significant predictors for TC (all p<0.05), including microcalcifications, hypoechogenicity, the prevalence of irregular margins, a taller rather than a wide form, high vascularity, and fast tumor growth. Multivariate analysis further showed that microcalcifications (odds ratio =21.37; p=0.024) and fast growth (odds ratio =22.70; p=0.021) were significant and independent factors associated with the risk of developing TC. Microcalcifications and fast growth of the TN could therefore be used as predictive factors for the development of TC in patients with AUS/FLUS.