As fine-needle aspiration techniques and diagnostic methodologies for thyroid nodules have continued to evolve and reporting systems have been updated accordingly, we need to be up to date with the latest information to achieve accurate diagnoses. However, the diagnostic approaches and therapeutic strategies for thyroid nodules vary across laboratories and institutions. Several differences exist between Western and Eastern practices regarding thyroid fine-needle aspiration. This review describes the reporting systems for thyroid cytopathology and ancillary studies. Updated reporting systems enhance the accuracy, consistency, and clarity of cytology reporting, leading to improved patient outcomes and management strategies. Although a single global reporting system is optimal, reporting systems tailored to each country is acceptable. In such cases, compatibility must be ensured to facilitate data sharing. Ancillary methods include liquid-based cytology, immunocytochemistry, biochemical measurements, flow cytometry, molecular testing, and artificial intelligence, all of which improve diagnostic accuracy. These methods continue to evolve, and cytopathologists should actively adopt the latest methods and information to achieve more accurate diagnoses. We believe this review will be useful to practitioners of routine thyroid cytology.
Background Follicular tumors include follicular thyroid adenomas and carcinomas; however, it is difficult to distinguish between the two when the cytology or biopsy material is obtained from a portion of the tumor. The presence or absence of invasion in the resected material is used to differentiate between adenomas and carcinomas, which often results in the unnecessary removal of the adenomas. If nodules that may be follicular thyroid carcinomas are identified preoperatively, active surveillance of other nodules as adenomas is possible, which reduces the risk of surgical complications and the expenses incurred during medical treatment. Therefore, we aimed to identify biomarkers in the invasive subpopulation of follicular tumor cells.
Methods We performed a spatial transcriptome analysis of a case of follicular thyroid carcinoma and examined the dynamics of CD74 expression in 36 cases.
Results We identified a subpopulation in a region close to the invasive area, and this subpopulation expressed high levels of CD74. Immunohistochemically, CD74 was highly expressed in the invasive and peripheral areas of the tumor.
Conclusions Although high CD74 expression has been reported in papillary and anaplastic thyroid carcinomas, it has not been analyzed in follicular thyroid carcinomas. Furthermore, the heterogeneity of CD74 expression in thyroid tumors has not yet been reported. The CD74-positive subpopulation identified in this study may be useful in predicting invasion of follicular thyroid carcinomas.
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The Asian Thyroid Working Group was founded in 2017 at the 12th Asia Oceania Thyroid Association (AOTA) Congress in Busan, Korea. This group activity aims to characterize Asian thyroid nodule practice and establish strict diagnostic criteria for thyroid carcinomas, a reporting system for thyroid fine needle aspiration cytology without the aid of gene panel tests, and new clinical guidelines appropriate to conservative Asian thyroid nodule practice based on scientific evidence obtained from Asian patient cohorts. Asian thyroid nodule practice is usually designed for patient-centered clinical practice, which is based on the Hippocratic Oath, “First do not harm patients,” and an oriental filial piety “Do not harm one’s own body because it is a precious gift from parents,” which is remote from defensive medical practice in the West where physicians, including pathologists, suffer from severe malpractice climate. Furthermore, Asian practice emphasizes the importance of resource management in navigating the overdiagnosis of low-risk thyroid carcinomas. This article summarizes the Asian Thyroid Working Group activities in the past 7 years, from 2017 to 2023, highlighting the diversity of thyroid nodule practice between Asia and the West and the background reasons why Asian clinicians and pathologists modified Western systems significantly.
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