Abstract
Thyroid nodules are a common finding in the adult population including the fact that more than 50% of individuals, over the age of 60, have thyroid nodules. The majority have been mostly detected with ultrasonography and 10% by palpation. The majority of these nodules are benign, whereas 5–15% of them are malignant. The pre-operative diagnosis of cancer is a critical challenge in order to ensure that each patient can be treated with the best tailored management with a reduction of unnecessary surgery for benign lesions. Fine needle aspiration cytology (FNAC) represents the first and most important diagnostic tool for the evaluation of thyroid lesions. According to the literature, FNAC is able to render a conclusive diagnosis in up to 70–80% of all cases. For the remaining 20–30% of nodules, cytological diagnoses fall into the category of indeterminate lesions mostly due to the lack of specific morphological features. According to the Bethesda system for reporting thyroid cytopathology (TBSRTC), indeterminate lesions can be sub-stratified into three different subcategories including “atypia of undetermined significance/follicular lesion of undetermined significance-AUS/FLUS”; “follicular or Hürthle cell neoplasm/suspicious for follicular or Hürthle cell neoplasm-FN/SFN”; and “suspicious for malignancy-SFM”. Many of these indeterminate lesions undergo repetition or diagnostic lobectomy. Nonetheless, the majority of these cases will have a benign diagnosis due to the fact that the rate of cancer ranges between 6 and 30%. It stands to reason that the application of ancillary technique, mostly molecular testing, emerged as a critical additional tool for those thyroid indeterminate lesions. Since the early 1990s, material collected from cytological samples yields sufficient and adequate cells for the detection of point mutation or gene fusions. Nonetheless, the further availability of new sequencing technologies such as next-generation sequencing (NGS) has led to more comprehensive molecular applications adopted now in clinical use. The current review investigates the multiple advances in the field of molecular testing applied in thyroid cytology.
Highlights
Papillary TC (PTC) and follicular TC (FTC) carcinomas arise from follicular cells and they constitute around 90% of all TC, generally with a very good prognosis [1,2,3,4,5,6,7,8,9,10]
Reporting data from their single academic tertiary center, Endo et al showed that genomic sequencing classifier (GSC) improved specificity and positive predictive value (PPV) while maintaining high sensitivity and negative predictive value (NPV) compared with gene expression classifier (GEC) in thyroid lesions diagnosed as AUS/FLUS and FN/SFN [87]
It is clear that the correct classification and diagnosis of indeterminate lesions of the thyroid is still a challenge in cytopathology practice
Summary
In the 1980s, fine-needle aspiration cytology (FNAC). is undoubtedly the first and most important pre-operative diagnostic procedure for the evaluation of thyroid lesions because of its advantages representing by its simplicity, safety, and cost-effectiveness. It is univocally stated that many papers have assessed the high diagnostic accuracy of molecular testing when applied on cytological samples [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34] In this perspective, the adoption of ancillary techniques, as an integrated tool for a conclusive diagnosis, has become an essential component in the management of several tumors due to the evidence that the knowledge of molecular mechanisms and genetics are linked with tumorigenesis and cancer in the thyroid gland. We summarize the role of molecular application in the different categories of the 2nd edition of TBSRTC
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