[399] A Single Institution Experience with the New Bethesda System for Reporting Thyroid Cytopathology: Correlation with Existing Cytologic, Clinical and Histological Data

Michele K McElroy, Mahooti Sepi, Farnaz Hasteh. University of California San Diego, San Diego, CA; VA San Diego Health Care System, La Jolla, CA

Background: The Bethesda system for reporting thyroid cytopathology (TBS) is a 6-tiered diagnostic system with specific recommendations for follow-up based on malignancy risk. The goal of this study was to compare it to the previously used classification system at our institution.
Design: 100 consecutive thyroid FNAs collected in 2006 were independently reviewed by two cytopathology-boarded pathologists. Diagnosis was based on TBS. Cases with discordant diagnoses were reviewed in a consensus conference for final diagnosis. Cases in which a final consensus could not be reached were excluded. Consensus diagnoses were compared to 2006 diagnoses, and were correlated with histologic and clinical follow-up.
Results: 97 cases were included in the study. Table 1 shows the distribution of cytology diagnoses. Interobserver agreement across all TBS categories was 0.4778. 28 cases had follow-up histology. Of these, 16 were benign and 12 were malignant. Of the cases called benign in 2006, 22 were called unsatisfactory in 2011. Cases were more likely to be unsatisfactory if there were < 3 passes or if there was no on-site pathology evaluation. Cases called follicular lesion in 2006 had both benign and malignant histology (12.5% malignant, 87.5% benign, n = 8). Clinical follow-up of these cases included repeat FNA (21%), resection (57%), imaging (36%) and none (21%). In contrast, all cases called follicular neoplasm in 2011 had actionable diagnoses by histology. The positive predictive value was 1.0 for actionable diagnoses in 2006 and 2011. The negative predictive value for an actionable diagnosis was 0.533 in 2006 and 2011.

Distribution of Cytology Diagnoses
benign (NAMC)59.8%42.3%
AUS (atypia)4.1%7.2%
follicular lesion14.4%n/a
follicular neoplasm1.0%7.2%
suspicious for malignancy2.1%0

Conclusions: Using strict TBS criteria for a satisfactory specimen increased the unsatisfactory rate. Fewer passes and lack of involvement of pathology in the procurement, preparation, and screening of slides led to increased unsatisfactory specimen. The inter-observer variability was in moderate agreement (kappa = 0.4778) using the Bethesda criteria. The pre-Bethesda diagnosis of follicular lesion led to inconsistent clinical management. More clarification is anticipated in clinical management for specific cytopathologic diagnostic categories using TBS.
Category: Cytopathology

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 63, Wednesday Afternoon


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