From the Guidelines
The initial approach for managing a thyroid follicular lesion of undetermined significance (FLUS) typically involves repeat fine needle aspiration (FNA) biopsy in 3-6 months, as recommended by the most recent guidelines 1. This category, also known as Bethesda Category III, represents about 15-30% risk of malignancy, warranting follow-up but not immediate surgical intervention. While waiting for repeat FNA, patients should undergo thyroid function tests to assess hormonal status, and ultrasound monitoring may be performed to evaluate for any changes in nodule size or characteristics. Some key points to consider in the management of FLUS include:
- The use of molecular testing, such as Afirma, ThyroSeq, or ThyGeNEXT, to further stratify malignancy risk if the repeat FNA yields the same FLUS result 1.
- The consideration of surgical consultation for possible diagnostic lobectomy for patients with multiple indeterminate FNAs or concerning clinical features, such as family history of thyroid cancer, radiation exposure, or nodule growth 1.
- The importance of a stepwise approach that balances the need to identify potential malignancies while avoiding unnecessary thyroid surgery for what are often benign nodules 1. It is essential to note that the management of thyroid nodules, particularly small ones, can be challenging due to the complexity and variability of guidelines 1. However, by following a coordinated and evidence-based approach, clinicians can provide optimal care for patients with thyroid follicular lesions of undetermined significance.
From the Research
Initial Approach for Managing Thyroid Follicular Lesion of Undetermined Significance
The initial approach for managing a thyroid follicular lesion of undetermined significance (FLUS) involves several steps, including:
- Fine-needle aspiration biopsy (FNAB) as the most accurate, safe, and cost-effective method for evaluation of thyroid nodules 2
- Classification of thyroid FNA results using the Bethesda system, which recommends repeat FNAB for FLUS due to its low risk of malignancy 2, 3
- Consideration of clinical and ultrasonographic features, such as hypoechogenicity and peripheral vascularization of the nodule, which may be predictive of malignancy 2, 4
Role of Repeat Fine-Needle Aspiration
Repeat fine-needle aspiration (RFNA) is effective in managing thyroid nodules diagnosed as FLUS, as it can help achieve a more definitive diagnosis and reduce the rate of benign nonneoplastic lesions 5, 6
- RFNA can reclassify a significant proportion of FLUS cases to a different category, such as benign, follicular neoplasm, or suspicious for malignancy 6
- The malignancy rate in FLUS cases with RFNA is similar to those without RFNA, suggesting that RFNA may not increase the detection of malignancy 6
Ultrasonographic Assessment
Ultrasonographic assessment of thyroid nodules can help guide clinical management after a cytologic diagnosis of FLUS, with features such as Mayo pattern classification and thyroid imaging reporting and data system scores being predictive of the final diagnosis 4
- Radiologist assessment of thyroid nodules in cases of FLUS can be highly predictive of the final diagnosis and can help guide management of thyroid nodules of this pathologic type 4
Management and Follow-up
The management and follow-up of FLUS cases involve a combination of clinical correlation, repeat FNA, and surgical excision, depending on the individual case and the results of the diagnostic tests 2, 3, 5, 6
- The National Cancer Institute (NCI) recommendations suggest that FLUS cases can benefit from repeat FNA to achieve a more definitive diagnosis, while cases suspicious for follicular neoplasm should undergo surgical excision for histologic characterization 5