EP53 – BRAF Mutation in Patients with Bethesda Cytological Indeterminate Thyroid Nodules: After reclassification of a variant thyroid carcinoma

      Maneeprasopchoke. P.1; Pongsapich, W.1; Poungvarin, N.2; Amornpichetkul, K.3, Metheetrairut, C.1; Piyawattayakorn, N.1; Vejvisithsakul, P.2; Chongkolwatana, C.1 1 Department of Otorhinolaryngology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand 2 Department of Clinical Pathology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand 3 Department of Pathology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand   Background: Fine needle aspiration biopsy (FNAB) is widely accepted as a tool for thyroid cancer risk stratification. Atypia of undetermined significant (AUS) and suspicious for malignant cell (SMC) have significant risk for papillary thyroid carcinoma. After the reclassification of a variant thyroid carcinoma, the term “Noninvasive follicular thyroid neoplasm with papillary-like nuclear features” (NIFTP)1 has recently been introduced. Objectives: To investigate clinical utility of BRAF mutation in Bethesda cytological indeterminate (AUS and SMC) thyroid nodules. Methods: A Cross-sectional study was conducted in 76 Thai patients with indeterminate nodules from July 2014 to October 2016. Pre-incisional FNAB was performed and sent for BRAFV600 analysis. Mutational status was studied by  direct sequencing and real time PCR techniques. The results were blinded to a pathologist who reviewed the final diagnosis. Results: BRAFV600 mutation was positive in 13/76 (17.1%) patients with 48.1% sensitivity and 100% specificity for cancer. The malignancy rate was 18.64% in AUS (11/59) with 8 papillary carcinoma, 2 NIFTP, and 1 follicular carcinoma, and 94.2% in SMC (16/17) with 14 papillary thyroid carcinoma and 2 papillary microcarcinoma. No BRAF mutation was noted in the NIFTP pathological report, which the patients were treated as papillary microcarcinoma. Conclusion: Malignancy rate in indeterminate nodule is high. With 100% specificity, BRAF mutation from FNAB has acceptable accuracy that can be part of surgical decision. Following the introduced reclassification, molecular diagnosis could likely be useful for nature of NIFTP. References:
    1. Nikiforov YE, Seethala RR, Tallini G, Baloch ZW, Basolo F, Thompson LD, et al. Nomenclature Revision for Encapsulated Follicular Variant of Papillary Thyroid Carcinoma: A Paradigm Shift to Reduce Overtreatment of Indolent Tumors. JAMA oncology. 2016

 

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