Absence of histological malignancy in a patient cohort with follicular lesions on fine-needle aspiration

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Abstract
Follicular lesions account for 4–6% of all thyroid fine-needle aspiration (FNA) cytologies. To date, no cytological criteria exist to distinguish follicular adenoma from carcinoma. For this purpose, histological evaluation after surgical exeresis is required. From 1993 to 2000 we performed 1238 US-assisted FNA biopsies in patients admitted to our unit for uni-or multi-nodular goiters. In the latter goiters, FNA was performed in the dominant nodule. Cytological examination revealed a follicular lesion in 71 patients (5.7%). All patients came from regions of Northern Italy with moderate iodine deficiency. In 48%, the lesion presented as a solitary nodule, while in the other 52% it occurred in the context of a multinodular goiter. Surgical exeresis of the neoplasm was recommended in all cases. Sixty-three patients (89%) underwent surgery (Group 1) while the other 8 patients (11%) opted for follow-up (Group 2). In Group 2, the mean nodule volume (3.2±0.5 ml) at baseline was slightly smaller (p=0.08) than that found in Group 1 (5.4±0.7 ml). In Group 1, histological examination after surgery showed a follicular adenoma in 52 patients (83%) and a colloid goiter in the others (17%). No malignancy was detected. Group 2 underwent a median follow-up of 46 months (range 24–96 months) on L-thyroxine suppressive regimen (dose range 75–125 μg/day), with TSH levels ranging from 0.1 to 0.3 mIU/l. Throughout the follow-up, no patient developed clinical or ultrasonographic features that could be considered worrisome for malignancy; thus, no further biopsy was performed. However, an overall slight increase (median +5.2%) in nodular volume in respect to baseline was observed. Although institutional and cytological bias cannot be ruled out, our data do not confirm the reported incidence of malignancy in histological specimens of follicular lesions diagnosed on FNA cytology, and prompt us to suggest a less aggressive first-step approach (i.e. careful clinical and instrumental evaluation, and suppressive LT4 therapy) for these lesions, unless anamnestic reports or clinical and ultrasonographic features of the nodules suggest malignancy.

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