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Fine needle aspiration (FNA) is currently accepted as an easy, safe, and reliable tool for the diagnosis of thyroid nodules. Nonetheless, a proportion of FNA samples are categorized into non-diagnostic or indeterminate cytology, which frustrates both the clinician and patient. To overcome this limitation of FNA, core needle biopsy (CNB) of the thyroid has been proposed as an additional diagnostic method for more accurate and decisive diagnosis for thyroid nodules of concern. In this review, we focus on the effectiveness and limitations of CNB, and what factors should be considered when CNB is utilized in the diagnosis of thyroid nodules.
Key Words: Thyroid; Neoplasm; Core needle biopsy; Ultrasonography
At present, thyroid nodules are a common problem. With advances in diagnostic technology and the widespread usage of high-resolution ultrasonography (US), approximately 19%-67% of otherwise healthy, asymptomatic individuals will eventually be found to have thyroid nodules.1 Out of the vast amount of thyroid nodules detected, only 7%-16% of them will be eventually diagnosed as malignant.1 Therefore, an accurate and efficient diagnostic tool is critical for triaging patients with nodular disease of the thyroid. Fine needle aspiration (FNA), especially under US guidance, is considered the gold standard for differential diagnosis of thyroid nodules, due to its simplicity, safety, cost-effectiveness, and diagnostic accuracy. Most authoritative guidelines recommend FNA for thyroid nodules detected on US as the next step in diagnosis.1,2 FNA has been reported to have diagnostic sensitivity of 83%-98% and specificity of 70%-92% by various studies.1-3
One major drawback of FNA is non-diagnostic and indeterminate cytology results (including atypia of undetermined significance/follicular lesion of undetermined significance [AUS/ FLUS], follicular neoplasm or suspicious for a follicular neoplasm [FN/SFN], and suspicious for malignancy), which comprises approximately 10%-33.6% and 15%-42% of all FNA samples,4-7 respectively. According to the Bethesda System for Reporting Thyroid Cytopathology,3 repeat ultrasonography-guided fine needle aspiration (US-FNA) is recommended for nodules with non-diagnostic or indeterminate cytology results, as repeat aspiration provides conclusive results in most of these nodules. However, about 9.9%-50% of nodules with initial non-diagnostic cytology,8-10 and 38.5%-43%' of nodules with indeterminate nodules11,12 will once again be diagnosed with inconclusive results, which induces frustration and anxiety in the patient and leads to confusion in patient management and additional diagnostic medical costs.
Core needle biopsy (CNB) of...