Application of Ultrasonography in Stratifying Malignancy Risk for Indeterminate Thyroid Nodules as per TBSRTC 2023

Abstract

Introduction: Thyroid nodules are extremely common and require complex management to prevent unnecessary surgical intervention and ensure that no malignant disease is overlooked. Several diagnostic tools and scoring systems are available to evaluate the risk of malignancy (ROM). The goal is to assess variables that can aid and support the clinical recommendations suggested by the updated Bethesda System for Reporting Thyroid Cytopathology (TBSRTC-2023), such as the ultrasonographic features of thyroid nodules, particularly for the indeterminate categories III (atypia of undetermined significance) and IV (follicular neoplasm). Methods: We retrospectively analysed the correlation of the demographic and ultrasonographic characteristics of thyroid nodules with the cytopathological and histopathological diagnoses of TBSRTC categories III (atypia of undetermined significance), IV (follicular neoplasm), V (suspicious for malignancy), and VI (malignant) in patients who underwent surgery in a single Portuguese centre over a 10-year period. Results: In total, 360 nodules were evaluated in 341 patients, and 57% were histopathologically malignant or borderline. The majority were included in the TBSRTC indeterminate categories III and IV, with ROMs of 44% and 43%, respectively. The ultrasonographic characteristics associated with a higher TBSRTC category and a greater ROM value were hypoechogenicity, the presence of microcalcifications, irregular margins, and the presence of cervical adenopathy. When correlating with a malignant histology, only adenopathy and the presence of microcalcifications were observed to be statistically significant. Discussion: The indeterminate categories of the TBSRTC have been the most challenging ones to manage. The new TBSRTC (2023) guidelines, as well as the ultrasonographic characteristics of a patient’s nodule, can be helpful in assessing the ROM and deciding on an appropriate course of treatment. Other resources, such as molecular tests, are also playing a more important role in the clinical decision process and may become crucial in the future. Conclusions: The worrisome ultrasound features that this study found to statistically correlate with a malignant histology were the presence of microcalcifications and adenopathy. The clinical management of thyroid nodules requires a careful analysis of clinical history and an evaluation of demographic details, personal and family history, ultrasonographic features, and the results of cytopathology, thyroid function, and molecular/genetic tests.