• Po-Sheng Lee, Jui-Yu Chen, Li-Hsin Pan, Chii-Min Hwu, Jen-Fan Hang, and Chin-Sung Kuo.
• Section of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
• Medicine (Baltimore). 2024 Aug 23; 103 (34): e39364e39364.

RationaleMolecular testing is becoming more widely used; however, the accuracy of diagnostic testing remains a primary consideration, especially for molecular testing that detects specific mutations associated with cancers.Patient ConcernsA 45-year-old female without documented comorbidities presented a thyroid nodule during a routine health examination. Initial evaluation revealed a 3.8-cm nodule in the left lobe of thyroid, classified as Bethesda System category III on fine needle aspiration cytology. Genetic molecular testing detected the BRAF V600E mutation via quantitative polymerase chain reaction assay, raising concern for papillary thyroid cancer (PTC).DiagnosesThe preoperative impression was PTC based on the detection of BRAF V600E mutation.InterventionsThe patient underwent thyroidectomy as well as lymph node dissection with the expectation to treat PTC.OutcomesThe final pathology unexpectedly revealed minimally invasive follicular carcinoma. Confirmatory Sanger sequencing unveiled a novel sequence variation involving nucleotide duplication within the range of 1794 to 1802, a non-V600E BRAF mutation not previously reported in follicular thyroid carcinoma.LessonsThis case study demonstrates the clinical relevance of exercising caution in molecular testing and its interpretation of results. For genetic testing used for diagnostic purposes, rigorous validation or cross-checking using different methods should always be considered to ensure appropriate interpretation of molecular results.Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.

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