EP44 – Institution-specific risk of papillary thyroid carcinoma based on preoperative fine needle aspiration biopsy: how do we compare to the Bethesda System?

      Mitchell, Brandon1; Eskander, Antoine2; Chiodo, Albino2; Hubbard, Bradley J.2; El-Masri, William S.A.2 1 Faculty of Arts and Sciences, Queen’s Universtiy, Kingston, Ontario, Canada 2 Department of Otolaryngology – Head and Neck Surgery, Michael Garron Hospital, Toroonto, Ontario, Canada   Background: The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) is presently used in surgical decision-making when interpreting the results of thyroid fine-needle aspirations (FNAs) based on six diagnostic categories that each has a unique malignancy risk. Recent studies have shown that due to the subjective nature of thyroid cytopathology interpretation, there is considerable variation in malignancy rates by institution, especially in the atypia/follicular lesion of undetermined significance  (AUS/FLUS) and follicular neoplasm (FN) categories. Objectives: To determine the institution-specific malignancy rates at a high volume endocrine surgery community-based hospital and its affiliated clinics.  These institution specific values can then provide better estimates for surgical decision-making. Methods: We conducted a three-year retrospective comparative analysis of fine needle aspiration cytology and final surgical pathology while controlling for important demographic and clinical variables. Results: Of 494 FNA cytology reports analyzed, 37.2% were benign, 23.3% were AUS/FLUS and 5.2% FN. Benign was associated with malignancy in 37.0%, AUS/FLUS in 66.7% and FN in 52.0%. The mean biopsied nodule size was significantly smaller among malignant (1.61 cm) compared to benign biopsies (2.81 cm). Discussion & Conclusion: We determined that the standard BSRTC suggested category frequencies and malignancy risks do not adequately represent BSRTC malignancy rates at our community thyroid practice. There is a higher than predicted malignancy rate associated with the AUS/FLUS and FN categories. To eliminate the subjective aspect interpreting thyroid cytology according to the BSRTC guidelines, institution-specific data should be provided to physicians and patients as decisions around the surgical management of nodules is made.   References:
    1. Bernstein, J.M., M. Shah, C. MacMillian, J.L. Freeman. 2016. Institution-specific risk of papillary thyroid carcinoma in atypia/follicular lesion of undetermined significance. Head & Neck 38:E1210-E1215.
    2. Cibas, E.S., and S.Z. Ali. 2009. The Bethesda system for reporting thyroid cytopathology. American Journal of Clinical Pathology 132:658-665.


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