Endocrine Abstracts

Introduction: The new Italian cytological classification of thyroid nodules published in 2014 has replaced the TIR3 ‘indeterminate’ category into two subcategory with different risk of thyroid cancer (TC): TIR3A, low-risk indeterminate lesion and TIR3B, high-risk indeterminate lesion. The aim of our study was to describe the incidence of TIR3B in a large prospective cohort of patients, the risk of TC, and its correlation with anamnestic, ultrasonographic (US) and cytological features.

Methods: Anamnestic, US and cytological features from all thyroid nodules undergoing FNA from June 2014 to January 2019 have been prospectively recorded. All patients receiving a cytological diagnosis of TIR3B have been referred to surgery and patients for whom histological examination was available have been divided into two groups: 1) TC; 2) benign lesions. Anamnestic, US and cytological features have been compared between the two groups.

Results: From June 2014 to January 2019, 1844 thyroid nodules underwent FNA in our institution and among these 96 (5%) have been diagnosed as TIR3B. Histological examination was available for 66 patients and among these 28 (42%) had TC and 38 (58%) had a benign lesion. At univariate analysis, patients aged ≤54 yrs had a significantly higher risk of TC than older ones (OR=7.9, 95% CI 2.45–25.42, P<0.001), as well as patients with family history for extrathyroid malignancy (OR=2.8, 95% CI 1.00–7.58, P=0.04) and for any malignancy (thyroid + extrathyroid) (OR=3.1, 95% CI 1.09–8.73, P=0.02) as compared to those with negative family history. At US, nodule size ≤20 mm (OR=5.6, 95% CI 1.84–17.10, P=0.02) and hyperechoic spots (OR=5.7, 95% CI 1.72–18.96, P=0.003) were significantly associated with TC. Among cytological parameters, nuclear grooves (OR=3.4, 95% CI 1.21–9.75, P=0.017), nuclear inclusions (P=0.002) and ‘frosted-glass core’ appearance (OR=5.1, 95% CI 1.69–15.45, P=0.003) had a significantly higher risk of TC. After multivariate analysis, age ≤54 yrs was found an independent risk factor for TC (OR 8.84, 95% CI 1.75–44.58, P=0.008).

Conclusions: Thyroid nodules with a TIR3B FNA diagnosis that turned out to be thyroid cancer at the histological examination were not larger than those who were benign at final diagnosis, but more often presented hyperecoic spots at US. Cytologically, these nodules more frequently exhibited nuclear grooves, inclusions and ‘frosted-glass core’ appearance. Patients harboring a malignant lesion were younger and had a family history for any malignancy. The combination of anamnestic, US and cytological features could help in discriminating which high-risk indeterminate specimens should effectively be referred to surgery.