Endocrine Abstracts

Introduction

The most cost-effective, minimally invasive and accurate tool to discriminate benign from malignant thyroid nodules is a fine-needle aspiration biopsy (FNAB). However, 2%–24% of FNABs provide non-diagnostic results, which are a clinical challenge, particularly when this result is recurrent.

Aim

To determine the predictive factors for recurrent non-diagnostic FNAB in thyroid nodules.

Methods

We present a retrospective study including all non-diagnostic FNABs of thyroid nodules, performed in our appoiment between january 2016 and december 2019. Demographic and clinical data, the number and location of nodules, their ultrasound characteristics and the respective EU-TIRADS classification, their cytological results according to Bethesda’s classification, and the moment when each FNAB was performed were recorded.

Results

Of a total of 1497 FNABs executed in the evaluated period, 494 (33.1%) were non-diagnostic. The FNAB was repeated in 225 (45.5%) nodules (76.4% in female’s patient with a median age of 59 years [P25-P75:48.5–68.5]), of which 108 (48.0%) presented again a non-diagnostic result; 43.6%, 7.5% and 0.9% had a benign, indeterminate and malignant cytological diagnosis. The presence of a single nodule shows to be an independent predictive factor to recurrent non-diagnostic FNAB (41.7% vs 23.9%; OR 2.270; 95% CI 1.282–4.021; P = 0.005). Nodules with benign ultrasound characteristics classified as EU-TIRADS 2 have a reduced risk of a repeated non-diagnostic cytology (1.9% vs 9.4%; OR 0.182; 95% CI 0.039–0.840; P = 0.029). Gender (P = 0.421), patient’s age (P = 0.632), cervical radiotherapy (P = 0.658), nodule’s location (P = 0.755), levothyroxine (P = 0.336) or anti-thyroid drugs treatment (P = 0.400) and time to repeat FNAB (P = 0.952) did not significantly influence the cytological result of the second biopsy. Despite without statistical significance, the recurrently non-diagnostic nodules appear to be larger (median larger diameter 24 mm [P25-P75:18–31] vs 21 mm [P25-P75:17–30]; P = 0.288).

Conclusion

In this study we concluded that the risk of a second non-diagnostic result was significantly higher in patients with single thyroid nodules. In contrast, the presence of a nodule corresponding to EU-TIRADS 2 classification reduce the probability of this outcome.