Thyroid nodules with a cytological diagnosis of follicular neoplasm (Bethesda IV): exploring approaches to risk stratification

Follicular neoplasm (IV category in the Bethesda reporting system) is the cytopathological diagnosis given when a fine-needle aspirate from a thyroid nodule reveals one of two abnormal cell patterns (non-oncocytic or oncocytic) with a similar risk of malignancy, approximately 30%. Bethesda IV accounts for up to 7-10% of fine-needle aspiration biopsy (FNAB) findings. Surgery remains the primary management strategy for Bethesda IV nodules in some medical centers, despite the fact that most of these lesions prove to be benign on histological examination. In light of the above, researchers have been actively seeking ways to refine the malignancy risk of follicular neoplasm for many years. The review summarises the results of a wide range of studies on the efficacy of different approaches to clarify the malignancy risk of follicular neoplasm, and analyses the prospects for their use in personalising patient management. Besides molecular testing, which has been the most advanced field in differential diagnosis of follicular neoplasm, risk stratification based on ultrasound features seems promising and requires further investigation. Despite the paucity of studies and lack of consensus in terms on methods, the cytological risk stratification of follicular neoplasm also appears to be a perspective approach, especially for its non-oncocytic subtype. In the future, the development of a diagnostic algorithm for the risk stratification of follicular neoplasm, incorporating the complex evaluation of ultrasound, genetic and cytological features, has the potential to reduce the number of unjustified surgical interventions by personalising the decision between surgery and active surveillance.