Evidence-Based Pathology: Risk of Malignancy Estimates Based Solely on Cytology and/or Surgical Follow-Up May Compromise the Forecasting Accuracy of Thyroid FNA
A Walts, R Gupta, S Bose, X Fan, D Frishberg, K Scharre, J Zhai, AM Marchevsky. Cedars Sinai Medical Center, LA, CA
Background: A National Cancer Institute (NCI) thyroid FNA panel recently recommended the diagnostic categories: unsatisfactory (U), benign (B), atypia of undetermined significance (US), follicular neoplasm (FN), and suspicious for malignancy (S), estimating risks of malignancy (RM) of <1%, 5-10%, 20-30% and 50-75% respectively.
Design: Our one-year experience with 927 thyroid FNA was reviewed using NCI diagnostic criteria. The number of malignancies diagnosed on follow-up FNA and/or surgery was used to calculate malignancy proportions in percentages. Malignancy proportions and relative risk (RR) of malignancy were calculated by NCI category using two denominators: entire cohort and cases with cytology or surgical follow-up information. Results obtained by the use of the two denominators and paired by NCI category were compared with chi-square statistics.
Results: Malignancy proportions and RR by NCI category using the 2 denominators are listed in Table 1. The differences in malignancy proportions and RR calculated using both denominators are significant for all categories (p=0.01).
Malignancy Estimates for NCI categories for the Entire Cohort and the Patients with follow up*All the patients followed up developed malignancy
|Category||Malignancy Estimates||Entire Cohort||Cases with cytology/Surgical follow up|
Conclusions: Our findings suggest that the risk of malignancy estimates provided in the NCI guidelines for thyroid FNA are amplified by the use of cytology or surgical follow-up information as the denominator in calculations. This method does not account for cases that have been lost to follow-up. Most studies in the literature have used this methodology, probably overestimating risk of malignancy. This problem needs to be considered in future studies.
Monday, March 9, 2009 1:30 PM
Platform Session: Section F, Monday Afternoon