To compare the ultrasonographic features of thyroid parenchyma of patients with Hashimoto thyroiditis (HT) concomitant with benign and malignant thyroid nodules to investigate if features of thyroid parenchyma can help diagnose malignant nodules in patients with HT.

A total of 456 patients who had HT concomitant with thyroid nodules and underwent thyroidectomy at Shanghai Ruijin Hospital between December 2012 and June 2019 were retrospectively included. The patients were divided into two groups: HT with benign nodules (n=175) and HT with malignant nodules (n=281). The size of the thyroid gland and echo type and blood supply of thyroid parenchyma were evaluated and compared between the two groups.

The anteroposterior diameter, transverse diameter, longitudinal diameter, and isthmus thickness of thyroid lobes in patients with malignant nodules were smaller than those in patients with benign nodules (P<0.01). The most common echo type of thyroid parenchyma in the malignant group was grid like changes (112/281, 39.9%), while the most common type in the benign group was micronodular hypoechoic changes (80/175, 45.7%). The percentages of patients with micronodular hypoechoic changes and nodular changes in the benign group were significantly higher than those in the malignant group (χ²=3.986 and 4.100, P<0.05). The percentage of patients with grid like changes in the malignant group was significantly higher than that in the benign group (χ²=4.818, P<0.05). The most common type of blood supply in the malignant group was normal or slight increase of blood supply (180/281, 64.1%), which was significantly more frequent than that in the benign group (64/175, 36.6%; χ²=32.748, P<0.01). In the benign group, moderately increased blood supply of the parenchyma is the most common type (85/175, 48.6%), which was significantly more frequent than that in the malignant group (61/281, 21.7%; χ²=35.753, P<0.01).

Evaluating the sonographic features of thyroid parenchyma is helpful to differentiate benign and malignant nodules in patients with HT. A smaller size of the thyroid gland and normal or slightly increased blood supply with grid like changes of the parenchyma often indicate a greater chance of having malignant nodules.