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Monday 8 April 2013

follicular lesion of undetermined significance

Fine-needle aspiration (FNA) for thyroid nodules is the most important method for determining a diagnosis.

In a study, 197 patients who underwent FNA for diagnostic evaluation of a thyroid nodule and had their results reported as a "follicular lesion of undetermined significance" (FLUS) using the Bethesda classification system. The final histopathologic breakdown was as follows: 32.9% of follicular adenoma, 41.1% of microfollicular adenomatoid nodule, (9.6% of microfollicular adenomatoid nodule on the background of thyroiditis, 8.6% of follicular carcinoma, 4.6% of follicular variant papillary carcinoma, and 3.1% of classic papillary carcinoma, for a 16.2% incidence of malignancy. Beyond these diagnoses in the FNA-biopsied nodules, 14.7% of incidental ipsilateral papillary thyroid microcarcinoma (PTM) and 6.6% of incidental contralateral thyroid lobe PTM have been observed. This study observed a 16.2% incidence of thyroid cancer in the nodule designated FLUS compared to the 5 to 15% rate reported by the Bethesda FNA classification. The overall incidence of incidental PTM in the thyroid gland was 21.3%. These data support considering surgical intervention for at least diagnostic purposes in a patient with the FNAB diagnosis of FLUS.


- Incidence of malignancy in thyroid nodules determined to be follicular lesions of undetermined significance on fine-needle aspiration. Teixeira GV, Chikota H, Teixeira T, Manfro G, Pai SI, Tufano RP. World J Surg. 2012 Jan;36(1):69-74. doi : 10.1007/s00268-011-1336-8 PMID: 22057754