Factors Associated with Malignancy in Patients with Maximal Thyroid Nodules ≥2 Cm.

Purpose: The relationship between large thyroid nodules and the risk of malignancy is controversial. This study aimed to examine the relationship between thyroid nodule size and the risk of malignancy of maximal thyroid nodules ≥2 cm and the risk of accompanied by occult thyroid carcinoma.

Methods: This was a retrospective study of patients who underwent near-total or total thyroidectomy for thyroid nodules from January 2016 to January 2019 at the First Affiliated Hospital,Zhejiang University School of Medicine. Clinical, biochemical, and pathological characteristics were examined for association with malignancy using univariable, multivariable, and receiver operating characteristic curve analyses.

Results: Finally, 367 patients (277 females (75.5%) and 90 males (24.5%)) with a mean age of 49.0±13.5 years were included. Multivariable logistic regression analysis showed that age (OR=0.959, 95% CI: 0.939-0.979, <0.001), Hashimoto's thyroiditis (OR=2.437, 95% CI: 1.162-5.112, =0.018), the diameter of maximal nodule (small) (OR=0.706, 95% CI: 0.541-0.919, =0.010), and punctate echogenic foci (OR=2.837, 95% CI: 1.598-5.286, <0.001) were independently associated with malignancy. Of 223 patients who had non-suspicious malignant nodules (TI-RADS <4), 12.7% (n=29) patients showed malignancy at postoperative pathology. Only age was associated with occult PTC in the univariable analyses (OR=0.962, 95% CI: 0.934-0.991, =0.011). When TPOAb was used as a continuous variable for statistical analysis, it showed a significant difference in the ROC curve, and the results showed TPOAb >31.4 mIU/L was more associated with occult PTC (=0.006). A predictive model including four independent risk factors of malignancy showed an optimal discriminatory accuracy (area under the curve, AUC) of 0.783 (95% CI=0.732-0.833).

Conclusion: Relatively young age (<54.5 years), Hashimoto's thyroiditis, the diameter of the maximal nodule, and punctate echogenic foci were independently associated with thyroid malignancy in patients with maximal thyroid nodules ≥2 cm. Young age (<54.5 years) and TPOAb >31.4 mIU/L were associated with occult PTC.