Notification of abstract acceptance
announced via E-mail on July 31st.
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Oct. 18 (Thu)  Grand Ballroom 101 Room - SS01 TH
09:40-09:50 [SS 01 TH-01] 
The US-FNA system for malignancy risk in thyroid nodules: 5-Tier classification
   
● Speaker Hyobin Seo (Seoul national university hospital Healthcare system Gangnam center)
● Authors Hyobin Seo,Dong Gyu Na2,Ji Hoon Kim3
● Affiliation Seoul national university hospital Healthcare system Gangnam center1,Human Medical Imaging and Intervention Center2,Seoul National University Hospital3
● PDF View  SS 01 TH-01.pdf

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PURPOSE:
To evaluate diagnostic performance of the US-FNA (UF) system for thyroid malignancy by comparing with the Bethesda (BE) system of thyroid cytopathology.

MATERIALS AND METHODS:
US-guided FNA was performed at 2049 thyroid nodules of 1210 consecutive patients. Among these nodules, a total of 704 nodules with final diagnoses (214 malignant and 490 benign nodules) were included for this study. The malignancy risk of thyroid nodules were classified into 4-tiers by US features. The UF system was stratified into 5-tiers of malignancy risk by combination of US-based 4-tier classification and 6-tier FNA results of BE system. The 5-tier malignancy risk of UF system was categorized as probably benign (BE category 1 with US-probable benign, low or intermediate risk nodule; all nodules with BE category 2), low risk (BE category 3 with US-probably benign or low risk nodules and category 4 with US-probably benign), intermediate risk (BE category 1 with US-high risk, BE category 3 with US-intermediate risk nodules, and BE category 4 with low risk nodules), high risk (BE category 3 with US-high risk nodules and BE category 4 with US-intermediate or high risk nodules), and probably malignancy (all nodules with BE category 5 or 6). The diagnostic performance of each system for predicting malignancy was calculated with receiver operating characteristics (ROC) analysis.

RESULTS:
The thyroid nodules were classified into 4 tiers by US-based stratification of malignancy risk; probably benign (risk<3%, n=101), low risk (≥3% and <15%, n=149), intermediate risk (≥15 and <50%, n=211), and high risk (≥50%, n=243). The FNA results were BE category 1 (n=35), category 2 (n=404), category 3 (n=89), category 4 (n=9), category 5 (n=92), and category 6 (n=75). In nodules with BE category 1, malignancy were found only in US-high risk nodules, and malignancy risk gradually increased according to US-based malignancy risk in nodules with BE category 3. The malignancy risk of nodules was classified by the UF system as probably benign (n=418, 1.4%), low risk (n=32, 12.5%), intermediate risk (n=52, 40.4%), high risk (n=35, 48.6%), and probably malignancy (n=167, 99.4%). In overall nodules, the area under the ROC curve of UF system (Az=0.972) was greater than that of the Bethesda system (Az=0.948) (P=0.08).

CONCLUSION:
The UF system may be more accurate and effective for predicting malignancy compared with the FNA BE system alone.

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