Hashimoto's Thyroiditis Does Not Affect Ultrasonographical, Cytological, and Histopathological Features in Patients with Papillary Thyroid Carcinoma.

The association between papillary thyroid carcinoma (PTC) and Hashimoto's thyroiditis (HT) is controversial. In this study, we aimed to compare preoperative thyroid functions, ultrasonography (US) features, fine-needle aspiration biopsy (FNAB) results, and histopathological characteristics of PTC in patients with and without HT. Data of 919 PTC patients were reviewed retrospectively. The diagnosis of HT was based on histopathological examination and patients were grouped as HT and non-HT. There were 1321 PTC lesions in 919 patients among which 317 (34.5 %) had coexistent HT. There were no significant differences in nodule volume, longitudinal diameter, texture, echogenicity, marginal regularity, presence of microcalcification and hypoechoic halo, and peripheral vascularization in patients with and without HT (p > 0.05, for all parameters). Macrocalcification was observed more frequently in the non-HT group (p = 0.021). FNAB results were similar in the two groups (p = 0.105). Distribution of variants, capsule invasion, vascular invasion, and extrathyroidal extension were observed with similar rates in the HT and non-HT groups. Lymph node metastasis was significantly higher in patients without HT (p = 0.012). Of the carcinomas, 66.1 % (n = 874) were papillary thyroid microcarcinoma (PTMC). Tumor size was lower in PTMC lesions coexistent with HT (p = 0.026). We observed lower rates of capsule invasion, extrathyroidal extension, and lymph node metastases in PTMC with HT compared to without HT (p = 0.007, p = 0.003, and p = 0.015, respectively). This study showed that US features, FNAB results, and histopathological findings of PTC lesions are not influenced by the presence of HT. However, PTMC seems to be related with less aggressive histopathological behavior in HT.