Endocrine Abstracts

Background: Current guidelines recommend repeat evaluation of a benign thyroid nodule after 1 to 2 years, which is only based on expert opinion. Objective data are needed to evaluate this recommendation.

Methods: This is a retrospective, descriptive study to describe the follow-up and incidence of malignancy in EU-TIRADS 3 nodules for which a fine needle aspiration cytology (FNAC) was indicated between 2017 and 2022. PET-positive thyroid nodules and thyroid nodules of which FNAC was indeterminate (Bethesda 1) were excluded.

Results: In total, 112 EU-TIRADS 3 nodules were included with a mean diameter of 3.17 ± 1.16 cm. Mean age of the study population was 54 ± 15 years with a female/ male ratio of 2.39. FNAC showed the following results; Bethesda 2 (97 nodules, 86.6%), Bethesda 3 (10 nodules, 8.9%), Bethesda 4 (4 nodules, 3.6%), Bethesda 5 (1 nodule, 0.9%), Bethesda 6 (no nodule). Of the 97 cases with Bethesda 2 classification, 13 cases underwent a total or hemithyroidectomy, 34 cases were followed for a median time of 24 (12-38) months and 50 cases were lost to follow-up. FNAC was repeated in 16 of the 34 cases which were in follow-up with the following results: Bethesda 1 (3 nodules, 18.8%), Bethesda 2 (11 nodules, 68.8%), Bethesda 3 (no nodule), Bethesda 4 (1 nodule, 6.3%), Bethesda 5 (1 nodule, 6.3%). The 2 nodules in which the repeat FNAC showed Bethesda 4 and 5 were resected and were benign. Anatomopathological examination of the 13 resected thyroid nodules with Bethesda 2 showed a malignancy in 2 cases of which one with distant metastasis. Of the 10 nodules with Bethesda 3, 5 underwent a thyroidectomy and all were benign. Of the 4 nodules with Bethesda 4, 3 underwent a thyroidectomy of which one nodule was malignant. The one case with Bethesda 5 underwent a thyroidectomy and showed a benign nodule.

Conclusion: In our single-center sample of EU-TIRADS 3 nodules only 3 (2.7%) cases had a pathology proven malignancy which is consistent to the given range described in the EU-TIRADS guidelines (2-4%). However, in 2 out of the 3 malignant thyroid nodules FNAC was benign (Bethesda 2). In the follow-up of 34 EU-TIRADS 3 nodules with Bethesda 2, 16 underwent a repeat FNAC of which 2 revealed a higher Bethesda classification which were eventually found to be benign on anatomic pathological examination.