[563] The Utility of Frozen Section in Surgical Management of Patients with Prior Indeterminate Thyroid FNA

Laura Nelsen, Melinda Lewis, George Birdsong, Talaat Tadros, Krisztina Hanley. Emory School of Medicine, Atlanta, GA

Background: Fine needle aspiration (FNA) is a safe and widely used diagnostic tool for evaluation of thyroid nodules, with a high accuracy in detection of papillary thyroid carcinoma (PTC). FNA results that fall into the atypical (Bethesda category III) or suspicious for PTC (Bethesda category V) remain a surgical dilemma. Intraoperative frozen section (FS) is often used to help guide the surgical choice of lobectomy vs total thyroidectomy. The accuracy of FS is limited due to sampling errors and freezing artifacts. We retrospectively reviewed cases of PTC diagnosed on thyroidectomy that had concurrent FS and FNA performed. Our goal was to assess the role of FS in patients with prior inconclusive or suspicious for PTC FNA diagnoses.
Design: We reviewed final surgical pathology (SP), FS and prior FNA results in cases diagnosed as PTC on resection specimens from 2008 to 2012. All FNA diagnoses were reclassified according The Bethesda System. Discrepancies in the SP, FS and FNA diagnoses were analyzed.
Results: 56 patients were included in the study.

FS↓ \ FNA→I Non-diagnosticII. BenignIII. AUSIV. Suspicious for FNV. Suspicious for PTCVI. MalignantTotal
Benign15511013
Atypical/Inclonclusive0120014
Follicular Lesion13133112
Malignant003451527
Total2911891756


In our institution FS was concordant with the SP diagnosis in 27% of AUS cases. In the suspicious for PTC category, 55% of patients underwent total thyroidectomy based on the FS diagnosis. Eight cases were misclassified on FNA as suspicious for FN, and 50% of these were called PTC on frozen section, requiring completion thyroidectomy.
Conclusions: FS has limited utility in intraoperative management of patient with prior AUS FNA. This can be explained by a 5-15% malignancy risk and that AUS represents a heterogeneous category, with subtle cytologic findings, which may not be appreciated on FS. The malignancy risk in suspicious for PTC is 60-75%, on FS only 50% of cases were correctly diagnosed. Follicular variant of PTC can be difficult to diagnose and may be misinterpreted as a FN on FNA. In our study, 50% of patients were diagnosed correctly as PTC, indicating that this category is diagnostically challenging. FS has limited utility in intraoperative management of patient with prior AUS FNA. This can be explained by a 5-15% malignancy risk and that AUS represents a heterogeneous category, with often subtle cytologic findings, which may not be appreciated on FS. While the malignancy risk in suspicious for PTC is 60-75%, on FS only 50% of cases were correctly diagnosed.
Category: Endocrine

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 45, Wednesday Afternoon

 

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