BACKGROUND
Thyroid nodules represent a common medical problem, affecting up to half of the population. However, most nodules are not cancerous (benign) as only ~5% of thyroid nodules are cancer. It is important to distinguish cancer from benign thyroid nodules in order to avoid excessive evaluation and unnecessary surgery. Biopsy of thyroid nodules, which became available in the late 1970s, is an accurate and safe test available to identify cancerous or suspicious thyroid nodules and the results of this test has been used to guide treatment. For example, thyroid nodules with cancer on a biopsy usually result in surgery while those with a benign result will be monitored by ultrasound for growth. Several improvements in thyroid biopsy have been developed over the years, including the increased use of ultrasound to guide the thyroid biopsy, improved resolution of ultrasound, increased standard reporting of the biopsy results, and improved techniques used in the evaluation of biopsy results. The goal of this study was to evaluate whether the diagnostic performance of thyroid biopsy has improved over the past four decades since its introduction.

THE FULL ARTICLE TITLE
Hsiao V et al 2022 Diagnostic accuracy of fine-needle biopsy in the detection of thyroid malignancy: A systematic review and meta-analysis. JAMA Surg. Epub 2022 Oct 12. PMID: 36223097.

SUMMARY OF THE STUDY
The authors searched the medical literature for Englishlanguage reports of studies that evaluated the thyroid biopsy accuracy and included at least 20 adult patients between 1975 and 2020. The data used for analysis included: age, gender, use of ultrasound-guidance during the thyroid biopsy, the cytopathology reporting system, accuracy of information, study period start and end, and income/development of the country where the study was performed. To account for the different cytopathology reporting systems used, all biopsy results were reclassified into one of four categories: benign, malignant, indeterminate, or non-diagnostic. The biopsy results were compared to a reference standard consisted of either the surgical pathology results for thyroid nodules removed surgically or results of follow-up thyroid ultrasounds for nodules initially characterized as benign.

Of the 1,023 eligible studies, 36 met the inclusion criteria. A total of 16,597 patients with an average age of 47.3 years were included, 79% being female patients. The overall accuracy of thyroid biopsy was 86%, while 7.2% of the results were non-diagnostic. Of the nondiagnostic biopsy results that went to surgery, 13.4% were cancerous. The diagnostic accuracy, proportion of non-diagnostic results, and rate of cancer of thyroid biopsies were not dependent of the time period when the study was performed. There was a high variability between the individual study results; however, none of the factors assessed could explain this finding, including the study period, type of reference standard used, cytological reporting system, use of ultrasonography, or being a study from a high-income country.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Thyroid nodule biopsy is a reliable diagnostic test for thyroid cancer with an overall acceptable diagnostic performance. Despite recent improvements in this procedure, its diagnostic accuracy and the rate of non-diagnostic results appear unchanged since its introduction more than four decades ago. Additional information regarding how patients are selected for the thyroid biopsy as well as the level of expertise of those performing this procedure and of those completing the cytological assessment might impact the overall diagnostic performance trends. Further studies should also evaluate the effect of the use of molecular markers and of the reclassification of a subset of papillary thyroid cancer into a new benign category, termed non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) on the thyroid biopsy results.

— Alina Gavrila, MD, MMSc

Table of Contents | PDF File for Saving and Printing