Fine‐needle aspiration of follicular patterned lesions of the thyroid: Diagnosis, management, and follow‐up according to National Cancer Institute (NCI) recommendations

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Abstract
The National Cancer Institute (NCI) State of the Science Conference on thyroid fine-needle aspiration (FNA) proposed that follicular patterned lesions can be divided into two diagnostic categories; follicular lesion of undetermined significance/Atypia of undetermined significance (FLUS/AUS) and suspicious for follicular neoplasm/follicular neoplasm (SFON/FON). The former group can benefit from repeat FNA (RFNA) to achieve a more definitive diagnosis and the latter should undergo surgical excision for histologic characterization (adenoma vs. carcinoma). In this study, we report the combined experience from our institutions with thyroid FNA cases that can be placed into NCI-designated thyroid FNA diagnostic categories for follicular patterned lesions. The case cohort comprised of 857 cases in 645 females and 212 males; 509 cases could be classified as FLUS/AUS and 348 as SFON/FON. Histologic follow-up was available in 273/509 (54%) cases diagnosed as FLUS/AUS and 251/348 (72%) cases diagnosed as SFON/FON. RFNA was performed in 203/509 (40%) patients classified as FLUS/AUS. RFNA diagnoses were: benign (125 cases), FLUS (46 cases), SFON/FON (20 cases), suspicious for papillary carcinoma (7 cases), papillary carcinoma (3 cases) and non-diagnostic (2 cases). The malignancy rate on surgical excision in the FLUS/AUS group was 27 and 15% with and without RFNA, respectively; and 25% in cases diagnosed as SFON/FON. RFNA is effective in managing thyroid nodules diagnosed as FLUS/AUS since the malignancy rates are different in cases with or without RFNA (27% vs. 15%). The malignancy rate (25%) in cases diagnosed as SFON/FON is similar to reported by other authors. Diagn. Cytopathol. 2010;38:731–739.