ODP485 Hyperthyroidism with Concurrent Thyroid Cancer: Causal Relation or Incidental Association?

INTRODUCTION: Thyrotoxicosis caused by Graves’disease (GD),toxic multinodular goiter (TMG) andtoxic adenoma (TA) can be associated with thyroid carcinoma; furthermore, tumors arisen in hyperthyroid tissue show an aggressive behavior (1). OBJECTIVE: To determine the incidence of thyroid carcinoma in thyrotoxic patients who underwent thyroidectomy and to analyzethe relationship between thyroid cancer, hyperthyroidism and outcomes of hyperthyroid versus euthyroid patients. MATERIALS AND METHODS: We retrospectively studied 304 consecutive hyperthyroid patients who underwent total thyroidectomy, presented in our institute between 2016 and 2021. The indications for surgery were GD (n=167, 3 of them were classified as Bethesda V on the basis of fine needle aspiration biopsy cytological examination prior to surgery), TMG (n=117) and TA (n=20). RESULTS: The incidence ofthyroid carcinoma in hyperthyroid patients was 18.1% (n=55) and was more common in patients with TMG (19.7%) and GD (18.6%), than in those with TA (5%). According to the post-surgical histological examination 41 patients were diagnosed with papillary thyroid carcinoma (92.7%), 2 patients were diagnosed with follicular thyroid carcinoma (3.6%), 1 patient with undifferentiated thyroid carcinoma (1.8%), and another patient with medullary thyroid carcinoma (1.8%). Papillary thyroid microcarcinoma accounted for 58.2% of all histological types. Lymph node involvement was found in 22% of the patients with GD, in 13% of those with TMG, and in none of those with TA. Distant metastases were found in 2 patients with GD and in other 2 patients with TMG. Compared with a similar group of 120 euthyroid patients who underwent surgery for thyroid cancer during the same time period, the patients with hyperthyroidism have a 3.4 times greater risk for developing lymphovascular metastases compared to euthyroid subjects (23.6% vs 8.3%, p=. 008). CONCLUSION: Our study showed that thyroid cancers in hyperthyroid patients have an aggressive behaviour, with a worse prognosis than ...