Ultrasonographic findings of papillary thyroid carcinoma with Hashimoto's thyroiditis

Papillary thyroid carcinoma (PTC) sometimes occurs with Hashimoto's thyroiditis (HT). It is often difficult to differentiate between benign and malignant nodules in HT because HT varies greatly on ultrasonography. We aimed to characterize the ultrasonographic features of PTC with HT.

In this retrospective study, 2167 patient records (1897 women and 270 men) were examined for ultrasonographic features and thyroid autoantibodies between 1998 and 2002 at our university. Patients with Graves' disease, positive TSH receptor autoantibody (TRAb) or thyroid-stimulating antibody (TSAb) were excluded. PTC was diagnosed by pathological examination.

Of the 1644 patients who were autoantibody negative (MCHA, TGHA, TgAb, TPOAb), 54 (3.3%) had PTC, while 29 (5.5%) of the 523 patients who were autoantibody positive had PTC. On ultrasonography, the frequency of dense calcification in patients with HT was significantly higher (P=0.0064) and frequency of psammoma bodies was less than PTC patients without HT (P<0.0001). On the other hand, PTC with HT had more irregular shapes and ill-defined edges of the borders with less hypoechogenecity and calcification than PTC without HT, but the difference was not significant.

The frequency of psammoma bodies in PTC with HT was less, while dense calcifications were greater than in those of PTC without HT. Any type of ultrasonographic calcification features may represent a risk for PTC.