Atypia of Undetermined Significance in Thyroid Fine-Needle Aspirations: Prognostic Value of Architectural and Cytologic Atypia
PA VanderLaan, JF Krane. Brigham and Women's Hospital, Boston, MA
Background: The atypia of undetermined significance (AUS) diagnostic category as defined in the 2007 National Cancer Institute (NCI) Thyroid Fine Needle Aspiration (FNA) State of the Science Conference is a heterogeneous category between benign and suspicious for malignancy. The clinical behavior of these lesions as a group is not well defined, nor is there significant data as to subgroup characteristics that may impart a higher risk of malignancy. Here, we report the prognostic significance of specific diagnostic features of AUS FNAs.
Design: All thyroid FNAs performed at Brigham and Women's Hospital from 1/05 to 4/09 with a diagnosis of AUS were analyzed retrospectively. As appropriate, our laboratory qualifies AUS as being due to cytologic or architectural atypia (or both). Follow-up data from repeat FNA or surgical resection were correlated with AUS qualifiers as well as any other diagnostic descriptors provided in the original report (atypia severity, specimen cellularity, number of atypical cells, presence of colloid, histiocytes, cyst lining cells, or Hurthle cell changes).
Results: A total of 306 thyroid AUS FNAs had conclusive follow-up data, stratified on the basis of atypia (see table). The risk of malignancy for architectural atypia alone (14%) was significantly lower than that observed for the other groups (Z=2.282, >95% CI): cytologic atypia (30%), both cytologic and architectural atypia (28%), or unspecified atypia (32%). No significant predictive value was noted for any of the other descriptive qualifiers, either with respect to AUS lesions overall or for any of the four atypia subcategories.
|Benign||55 (86%)||38 (70%)||58 (72%)||73 (68%)||224 (73%)|
|Malignant||9 (14%)||16 (30%)||22 (28%)||35 (32%)||82 (27%)|
|Total||64 (21%)||54 (18%)||80 (26%)||108 (35%)||306|