Risk of malignancy in thyroid nodules with atipia of undetermined significance

Prevalence of malignancy among cytologies with atypia of undetermined significance (Bethesda category III) is variable, ranging from 5%-37% in the different studies. There is thus no agreement on whether FNA should be repeated or surgery should be performed in these cases. The aim of this paper was to analyze the risk of malignancy in order to establish the most adequate clinical approach.

We analyzed 431 thyroid cytologies performed at our hospital since the introduction of Bethesda System (from January 2011 to September 2014), of which 32 (7.1%) were labeled as category III. The second FNA, when performed, and the histological results after surgery were reviewed.

Twenty-three patients (82.1%) underwent thyroidectomy, while repeat FNA was performed in the remaining 5 patients (17.9%). Cytology was reported as benign (category II) in 3 (60%) and as unsatisfactory (category I) in 2 (40%), who underwent thyroidectomy. Thirteen of the 25 (52%) surgical thyroid specimens showed no malignancy, while differentiated thyroid carcinomas were found in 12 (48%): papillary cancer in 10 (83.3%), follicular cancer in 1 (8.3%), and papillary cancer with follicular areas in 1 (8.3%). The risk of malignancy of Bethesda category III in our patients was 42.9%-48.0%.

We recommend thyroidectomy for all patients with of cytological Bethesda category III.