Fine needle aspiration biopsy of thyroid nodule smaller than 1.0 cm: accuracy of TIRADS classification system in more than 1000 nodules.

Objective: To identify whether or not the same ultrasound features can be applied and should be considered to support the decision as to which subcentimeter nodules should be biopsied with fine needle aspiration (FNAB).

Methods: Single-institution, IRB approved, retrospective study conducted from 2008 to 2016 that evaluated 1094 thyroid nodules smaller than 1.0 cm that were classified according to TIRADS and submitted for FNAB.

Results: The value of FNAB of thyroid nodules smaller than 1.0 cm were assessed and correlated with the sonographic criteria by comparing the obtained results with the cytological findings in 1094 thyroid nodules. In the analysis considering all nodules, the proportion of malignancies among nodules with TIRADS 2 is 0.91% and for TIRADS 3 is 2.87%. Among those classified as 4A, 12.26%; with 4B classification, 34.43%; with 4C classification, 66.6%; and among those with 5 classifications, 85.7%.

Conclusion: In conclusion, the TIRADS classification system, based on the sonographic features reported herein, may help detect which nodules should be investigated for potential malignancies. Advances in knowledge: Few reports compare the efficacy of ultrasound-FNAB for thyroid nodules smaller than 1.0 cm in diameter. The findings of malignancy in this subgroup of nodules may help in the clinical follow-up of which patients should be submitted to an early imaging evaluation or intervention.