Endocrine Abstracts

Introduction

Recent published studies suggest that the anatomical location of the thyroid nodule may be associated with different risks of malignancy. However, the results are still sparce and little consensual.

Aim

To evaluate the frequency of nodules on different locations of the thyroid gland and to determine whether their location correlates with different malignancy risks.

Methods

We present a retrospective study including all Fine-Needle Aspiration Biopsies (FNABs) performed in our department between January 2016 and December 2019. Demographic 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 their histology were recorded. The nodule was considered benign in the presence of benign cytology or histology, and malignant when this diagnosis was confirmed histologically.

Results

From a total of 1497 FNABs included, performed in 1046 patients, 1004 had definitive diagnoses (934 [89.5%] benign; 70 [6.7%] malignant). The majority (86%) were done in female patients, with a median age of 56 years (P25–P75:47–66). The presence of a single thyroid nodule was associated with a higher rate of malignancy when compared to multinodular goiter (34.3% vs 22.1%, P = 0.019). The right lobe was the location with the highest description of nodules (452 ​​[45.0%]), followed by the left lobe (425 [42.3%]) and the isthmus (127 [12.6%]). There were no differences regarding the risk of malignancy between these locations (7.7% vs6.4% vs 6.3% respectively; P = 0.686). In 686 patients, the longitudinal nodular position was documented (424 [61.8%] in the middle lobe; 206 [30.0%] in the lower lobe; and 56 [8.2%] in the upper lobe). Likewise, the rate of malignant lesions was not significantly more prevalent in any of these positions (8.0% vs 6.3% 10.7%, respectively; P = 0.514).

Conclusion

Although current literature has shown that thyroid nodule location can be an independent risk factor for a malignant lesion, our study could not confirm these data. In this large cohort of FNABs samples, we evidenced that there is no relationship between the anatomical location of the thyroid nodule and its risk of malignancy. Despite little consensus on this subject, some studies suggest that the isthmus and the lower lobe nodules have the highest risk, while others show this result in the middle lobe.