[406] Outcomes in Thyroid Fine-Needle Aspiration with Atypical Follicular Cells: Risks of Malignancy and Integration into the Bethesda System for Reporting Thyroid Cytology.

Martin H Luu, Andrew H Fischer, Latha R Pisharodi, Christopher Owens. University of Massachusetts Memorial Medical Center, Worcester; Rhode Island Hospital, Providence

Background: The recently proposed Bethesda System (TBS) for reporting thyroid fine-needle aspiration (T-FNA) is a system intended to standardize terminology and offers specific cytologic categories to facilitate more useful reporting, data sharing and increased knowledge of the inherent risk of malignancy to optimize patient care. It has been suggested that the Bethesda category 'atypical follicular cells' actually encompasses four (4) subcategories that may have different risks of malignancy. In this study, we sought to determine whether or not there are significant differences in the risks of malignancy between the suggested subcategories of 'atypical follicular cells.'
Design: All ThinPrep® T-FNA between 2006 – 2008 at our institution with a cytologic diagnosis of 'atypical follicular cells' were retrieved and subclassified into one of four subcategories: 1) atypia, NOS; 2) atypia, rule out follicular neoplasm; 3) atypia, rule out Hurthle cell neoplasm; and 4) atypia, rule out papillary carcinoma. Histologic follow-up data were tabulated for each subcategory. The risks of malignancy were calculated and comparisons were made between the 'atypical follicular cells' subcategories. Categorical analysis was performed using a 2-tailed Chi-square test and a p-value of 0.05 was considered significant.
Results: A total of 2101 T-FNA cases were retrieved with 475 histologic follow-ups. A total of 186 (9%) were originally classified as 'atypical follicular cells,' and 164 (88%) had histologic correlation with an overall risk of malignancy of 23%. The risk of malignancy for atypical follicular cells subcategorized as 'atypia, rule out papillary carcinoma' was significantly higher (45%) than the other subcategories (p = 0.026). Cases subclassified as 'atypia, rule out follicular neoplasm' and 'atypia, rule out Hurthle cell neoplasm' did not have significantly different risks of malignancy (p = 0.5).
Conclusions: The subcategory 'atypia, rule out papillary carcinoma' has a significantly higher risk of malignancy when compared to the other atypical follicular cells. Cytologists should strive to communicate the risk of this subcategory to surgeons and clinicians when interpreting 'atypical follicular cells' in thyroid FNA.
Category: Cytopathology

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 60, Wednesday Afternoon

 

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