Evidence-Based Pathology: A Review of Best Evidence Supporting the Value of Thyroid FNA To Predict Risk of Malignancy
AM Marchevsky, R Gupta, S Bose, X Fan, D Frishberg, K Scharre, A Walts, J Zhai. Cedars Sinai Medical Center, LA, CA
Background: A National Cancer Institute (NCI) thyroid FNA panel recently recommended standardized diagnostic categories: benign (B), atypia of undetermined significance (US), follicular neoplasm (FN), and suspicious for malignancy (S) with risks of malignancy (RM) of <1%, 5-10%, 20-30% and 50-75% respectively.
Design: The best evidence supporting these RM was reviewed to determine: evidence level, whether the data were based on clinical follow-up (FU) of most patients in each cohort or on repeat cytology or surgery FU information gathered from selected cases and whether any standard risk estimates such as relative risk (RR) or others were provided.
Results: The best evidence cited as references in the NCI guidelines include 4 well-designed level III studies and a review article. These studies reported retrospective experience with 7667 thyroid FNA. None of the studies provided clinical follow-up for a significant number of patients in the B, US and FN categories. Only 1 study provided cytologic follow-up for B cases and reports 15 malignancies in 2526 FNA initially reported as B. None of the studies provided RR or other risk estimates.
Conclusions: Current estimates of malignancy risk provided by the NCI expert panel probably overestimate the possibility of subsequent thyroid malignancy in patients with FNA showing B, US and FN lesions. Current RM estimates are not based on studies where entire populations were followed-up and may be subject to sample bias as they do not include information from patients lost to follow-up. Proportions of malignancy derived from cytology and/or surgical follow-up data should be used as an accurate substitute for risk of malignancy.
Wednesday, March 11, 2009 1:00 PM
Poster Session VI # 39, Wednesday Afternoon