Atypia of undetermined significance on thyroid fine needle aspiration: surgical outcome and risk factors for malignancy.
OBJECTIVE
This study was performed to analyze the surgical pathology results of the "atypia of undetermined significance" (AUS) category from thyroid fine needle aspiration (FNA) and to describe the characteristics to distinguish a malignant from a benign nodule.


METHODS
A retrospective analysis was done on 116 patients who underwent thyroid surgery from December 2008 to December 2012, following a diagnosis of AUS from preoperative thyroid FNA. We investigated the age, gender, size and site of the nodules, ultrasonographic criteria, cytological features, the number of atypia results after repeated FNAs, surgical method, and final pathologic results.


RESULTS
Sixty-five out of 116 patients underwent total thyroidectomy and the rest had partial thyroidectomy. The final pathologic results were 41 malignancies (35.3%) and 75 benign diseases (64.7%). AUS was divided into group 1: 'cannot rule out malignancy' or group 2: 'cannot rule out follicular neoplasm'. After surgery, group 1 revealed papillary thyroid cancer in most cases and group 2 revealed follicular adenoma in most cases. Age over 40 years, ultrasonographic findings suggestive of malignancy, more than 2 results of atypia from repeated FNAs and nodules less than 2 centimeters were risk factors for malignancy on univariate analysis. Multivariate analysis showed that ultrasonographic findings suggestive of malignancy was a significant risk factor for malignancy.


CONCLUSIONS
For proper evaluation of the risk for malignancy in thyroid AUS patients, the ultrasonographic criteria should be considered along with other clinicopathological findings such as age, nodule size, number of atypia, cytologic features.
Department of Surgery, Chonnam National University Medical School, Gwangju, Korea.
Young Jae
YJ
Ryu
Department of Surgery, Hyundai Hospital, Gwangju, Korea.
Youn Seung
YS
Jung
Department of Surgery, Chonnam National University Medical School, Gwangju, Korea.
Hyun Chul
HC
Yoon
Department of Surgery, Chonnam National University Medical School, Gwangju, Korea.
Min Jung
MJ
Hwang
Department of Surgery, Chonnam National University Medical School, Gwangju, Korea.
Sun Hyoung
SH
Shin
Department of Surgery, Chonnam National University Medical School, Gwangju, Korea.
Jin Seong
JS
Cho
Department of Pathology, Chonnam National University Medical School, Gwangju, Korea.
Ji Shin
JS
Lee
Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.
Hee Kyung
HK
Kim
Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea.
Ho Cheol
HC
Kang
Department of Radiology, Chonnam National University Medical School, Gwangju, Korea.
Hyo Soon
HS
Lim
Department of Surgery, Chonnam National University Medical School, Gwangju, Korea.
Jung Han
JH
Yoon
Department of Surgery, Chonnam National University Medical School, Gwangju, Korea.
Min Ho
MH
Park
Atypia of undetermined significance; Fine needle aspiration; Thyroid neoplasms