Prevalence of thyroid cancer in patients with hashimoto’s thyroiditis with or without nodules at the first clinical evaluation and in the subsequent follow-up.

BACKGROUND: Several surgical and pathological studies suggest a significant association between Hashimoto’s thyroiditis (HT) and thyroid cancer, but this relationship is still elusive and often not confirmed by non-surgical series. In this study we compared the prevalence of thyroid cancer in HT associated to thyroid nodules vs HT without thyroid nodules at the first diagnosis and during the subsequent follow-up. PATIENTS AND METHODS: A total of 484 patients with a diagnosis of HT at their first clinical evaluation were subdivided into two groups: 243 HT patients without thyroid nodules (HTN-) and 241 with one or more nodules (HTN+). FT3, FT4, TSH Tg/TPO-autoantibodies and thyroid ultrasound were performed in all cases; fine needle aspiration cytology (FNAC) were performed in 155 patients with thyroid nodules and 74 patients underwent surgery. RESULTS: HTN+ patients displayed a high prevalence of suspicious/malignant cytology (Tir 4-5) (44/152 = 28.9%); indeterminate (Tir-3) cytology was found in 47/152 (30.9%). In the 74 HTN+ patients submitted to thyroidectomy, a high rate of malignancy was documented (48/74 = 64.9%). The histotype distribution was 44 papillary (PTC), 2 follicular (FTC), 2 medullary (MTC) thyroid carcinomas, PTC being the only tumor significantly associated to HT. A high prevalence of multicenter PTC was also found (14.4%) in this group. In the HTN- group, a minority (22/130 = 17%) of patients with available follow-up (1-9 years) developed one or more thyroid nodule, but only 3 of them required FNAC which resulted benign (Tir-2) in all cases. None of these patients was submitted to thyroidectomy. CONCLUSIONS: This study confirms a high prevalence of thyroid cancer (mostly PTC) in patients with HT associated to thyroid nodules at the first clinical evaluation. Conversely, no evidence of increased prevalence of thyroid malignancy was found in patients with HT without associated nodules at the first clinical evaluation during the first years of follow-up. Although this observation requires further investigations, it might provide a clue to understand the marked differences in the association rate between HT and thyroid cancer reported in surgical and not-surgical studies.