[416] The Sequential Application of Immunocytochemistry, BRAF-1 and N-RAS Mutation Analysis Identifies Malignant Follicular Thyroid Neoplasms on Liquid-Based Cytology

Esther D Rossi, Maurizio Martini, Patrizia Straccia, Sara Capodimonti, Celestino P Lombardi, Alfredo Pontecorvi, Valerio G Vellone, Gian F Zannoni, Luigi M Larocca, Guido Fadda. Catholic University, Rome, Italy

Background: Fine-needle aspiration cytology (FNAC) is an important tool for evaluating thyroid nodules but up to 20% of cases may result in an indeterminate diagnosis (Follicular Neoplasm – FN and Follicular Lesion of Undetermined Significance – FLUS). Some molecular alterations of specific pathways involved in the oncogenic process, namely BRAF and RAS mutations, are referred as markers of malignancy for papillary carcinoma (PTC). BRAF mutations have been identified in about 50% of PTC, mostly classic variant, while studies have demonstrated that RAS point mutations may also occur in thyroid carcinomas. In indeterminate and suspicious for carcinoma thyroid lesions (SC) we studied a panel including Immunocytochemistry (ICC) and BRAF mutational analysis followed by N-RAS in BRAF wild-type (wt) cases.
Design: In 2011-2012, 20 cases diagnosed as FN/FLUS (9 Benign and 11 malignant at histology) and 37 SC (7 Benign and 30 malignant lesions) processed with liquid-based cytology (LBC, ThinPrep, Hologic, USA) were diagnosed at the Catholic University of Rome (Italy). All 57 cases underwent HBME-1 and Galectin-3 and mutation analysis of BRAF. The 46 cases negative for BRAF underwent N-RAS codon 61 mutation analysis. ICC as well as DNA extraction were performed on LBC-stored material.
Results: Out of 57, 36 cases (11 FN/FLUS and 25 SC) showed an ICC positivity, 11 of them 25 SC showed a BRAF (44%). Out of the 46 BRAF-wt cases, 3 had N-RAS mutation (6%). In FN/FLUS all ICC positive cases resulted PTC whereas 2 cases showed a N-RAS mutation. In the 30 malignant SC, ICC resulted positive in 84.6% with 36% BRAF and 1 RAS mutations. All 3 RAS-mutated cases resulted as Follicular variant of PTC (FVPTC).
Conclusions: The sequential application of ICC and mutational analysis on LBC may enhance the accuracy of FNA and its cost-effectiveness. ICC identifies more malignancies in the FN/FLUS group, especially when supported by RAS analysis, whereas cases negative for ICC can benefit of a strict follow-up instead of surgery. In SC, BRAF and RAS represent strong indicators of malignant outcome and may warrant a more aggressive surgical approach.
Category: Cytopathology

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 70, Tuesday Afternoon


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