[590] The Value of Thyroid Atypia of Undetermined Significance (AUS) Terminology and Its Follow-Up by Repeat FNA

SH Zydowicz, A Kemp, E Lucas, X Lin, R Nayar. Northwestern University, Chicago, IL

Background: Since 2001, we have used a 6-tier system to report thyroid FNA with 3 “indeterminate” categories and repeat FNA (rFNA) for follow-up of the Atypia of Undetermined significance (AUS) category. We further sub-categorize AUS as “morphologic” (AUS-M) and “adequacy related” (AUS-A). With increasing acceptance of rFNA for AUS, we assessed compliance with follow up and the malignancy outcomes of AUS, Neoplasm and Suspicious.
Design: All thyroid biopsy reports between June 2006 and June 2009 were retrieved from our files. Data was analyzed and correlated with surgical outcomes.
Results: 4242 adequate thyroid FNA's were categorized as shown in the Table. Follow-up FNA was done in 319 (37%) of patients first diagnosed as AUS. A definitive diagnosis was made in 192 (60%) with rFNA. On rFNA, 113 (35%) remained as AUS of which 46 had surgery and 12 (26%) were malignant. In comparison, 66% Neoplasm and 84% Suspicious cases underwent surgery. Malignancy outcomes were AUS-overall 7%, Neoplasm 17% and SUSP 63%. When AUS outcomes were assessed by subtype and whether rFNA was done prior to surgery, the malignancy rate was 21% in AUS-A versus 6% in AUS-M cases, and 26% in AUS resected after an AUS rFNA versus 2% in AUS cases that went directly to surgery after the first AUS diagnosis.

Distribution of Thyroid Biopsies from June 2006 through June 2009

	Total Number of Cases	Number of resected cases	Negative for Malignancy	Neoplasm	Positive for Malignancy
Negative	2940 (70%)	190 (65%)	153 (80%)	33 (17%)	3 (2%)
Other	855 (20%)	332 (39%)	189 (57%)	119 (36%)	24 (7%)
"Morphologic"	695	298 (43%)	168 (57%)	113 (38%)	17 (6%)
"Adequacy"	160	34 (21%)	21 (62%)	6 (18%)	7 (21%)
Neoplasm	212 (5%)	140 (66%)	43 (20%)	68 (32%)	25 (17%)
Suspicious	49 (1%)	41 (84%)	5 (12%)	10 (24%)	26 (63%)
Positive	186 (4%)	152 (82%)	0	3 (2%)	153 (98%)

Conclusions: (1) AUS is a valuable subcategory in thyroid FNA reporting with a lower malignancy outcome (7%) than Neoplasm (17%) and Suspicious (63%). (2) Repeat FNA for AUS definitively categorizes over half of cases first interpreted as AUS (59%) (3) Over half (53%) of AUS on repeat FNA were Negative and did not need surgery (4) The malignancy rate in cases diagnosed as AUS on repeat FNA (26%) is higher than that of the Neoplasm category (17%) and thus these cases need resection (5) “Adequacy related” AUS cases have a higher malignancy rate than “morphologic” AUS (21% versus 6%), emphasizing the importance of not downgrading suboptimal cases to Negative.
Category: Endocrine

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 40, Tuesday Afternoon