Hashimoto's thyroiditis - an independent risk factor for papillary carcinoma

Abstract Introduction: The link between Hashimoto's thyroiditis and thyroid carcinoma has long been a topic of controversy. Objective: The aim of our study was to determine the prevalence of thyroid carcinoma and Hashimoto's thyroiditis coexistence in histopathologic material of thyroidectomized patients. Methods: In a retrospective study, the clinicohistopathologic data of 2117 patients (1738 females/379 males), who underwent total or partial thyroidectomy for thyroid gland disorder at a single institution from the 1st of January 2005 to the 31st of December 2014 were analyzed. Results: Thyroid carcinoma was detected in 318 cases (15%) and microcarcinoma (thyroid cancer ≤10 mm in diameter) was found in permanent sections in 169 cases (8%). Hashimoto's thyroiditis was detected in 318 (15%) patients. Hashimoto's thyroiditis was significantly more often associated with thyroid carcinoma and microcarcinoma compare to benign condition (p = 0.048, p = 0.00014, respectively). Coexistence of Hashimoto's thyroiditis and thyroid carcinoma/thyroid microcarcinoma did not affect tumor size (p = 0.251, p = 0.098, respectively), or tumor multifocality (p = 0.831, p = 0.957, respectively). Bilateral thyroid microcarcinoma was significantly more often detected when Hashimoto's thyroiditis was also diagnosed (p = 0.041), but presence of Hashimoto's thyroiditis did not affect bilateral occurrence of thyroid carcinoma (p = 0.731). Conclusion: Hashimoto's thyroiditis is associated with significantly increased risk of developing thyroid carcinoma, especially thyroid microcarcinoma.