Clinical Thyroidology® for the Public
Summaries for the Public from recent articles in Clinical Thyroidology
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THYROID NODULES
Core needle biopsy for evaluation of thyroid nodules
BACKGROUND
Thyroid nodules are very common and identified in up to 50% of the population. Only about 5-6% are cancers and the rest are benign (noncancerous), so most patients will not need surgery of these nodules unless they have symptoms. Thyroid biopsy is the main test used to determine whether a given nodule needs to be removed. Thyroid biopsy is usually done with a thin needle (fine needle biopsy) and is a well-tolerated procedure with minimal to no complications and can be done in the office. However, up to 10% of thyroid fine needle biopsies will not have enough cells for a diagnosis. In addition, as many as 25% will be indeterminate, meaning they can’t tell if the cells are normal or abnormal. There are 3 indeterminate categories: 1) atypia of unknown significance or follicular lesion of unknown significance (AUS/ FLUS), 2) follicular or hurtle cell lesion and 3) suspicious for papillary cancer. AUS/ FLUS is the most common indeterminate finding and additional testing such repeat biopsy and the use of molecular markers is often used to determine the cancer risk.
An alternative method to evaluate thyroid nodules is a core needle biopsy (CNB). This procedure uses a large needle and requires an experienced operator with specific training. CNB also has a higher risk of complications than a fine needle biopsy, including injuries to the trachea and carotid artery.
Many organizations have supported the use of CNB as a second line test when a fine needle biopsy is not diagnostic. However, in Asia, many institutions recommend the use of CNB as an initial test because of its reported lower incidence of non-diagnostic results. This study was performed to compare the use of CNB vs a fine needle biopsy as a first option in the evaluation of thyroid nodules.
THE FULL ARTICLE TITLE
Ahn HS et al 2021 Diagnostic performance of core needle biopsy as a first‐line diagnostic tool for thyroid nodules according to ultrasound patterns: Comparison with fineneedle aspiration using propensity score matching analysis. Clin Endocrinol (Oxf) 94:494–503. PMID: 32869866.
SUMMARY OF THE STUDY
This is study comparing the results of CNB, used as the initial test in one institution, to the results of a fine needle biopsy from two other institutions in Korea. In the first institution CNB was used as an initial test in 705 patients whose ultrasound predicted the likelihood of a non-diagnostic a fine needle biopsy.
This was compared to a second group of 583 patients from the other two institutions where a fine needle biopsy was the initial testing. Ultrasound features of the thyroid nodules were categorized according to the Korean Thyroid Imaging Reporting and Data System (K-TIRADS). Nodules were considered cancerous either by result of CNB or a fine needle biopsy, or by the evaluation of the nodule after surgery. Nodules were considered benign if there were two benign results on CNB or a fine needle biopsy, or one benign result on CNB or a fine needle biopsy and no evidence of indeterminate or cancer results in initial or repeat biopsy or in a surgical pathology result.
CNB was less likely to result in a nondiagnostic, AUS/ FLUS or suspicious for malignancy cytology diagnosis than was a fine needle biopsy. CNB also had a higher frequency of cancer cytology findings than a fine needle biopsy. The a fine needle biopsy group had a small number of false negative results (2 of 244 nodules) and one false positive result (1 of 141 nodules). There were no false negative or false positive results in the CNB group.
There were no complications in the fine needle biopsy group. A total of 5 patients in the CNB group developed local bleeding treated just with manual pressure. The authors concluded that CNB was superior to a fine needle biopsy in the initial evaluation of thyroid nodules.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study suggests that increased use of CNB may be able to decrease the incidence of inadequate or indeterminate results when a fine needle biopsy is used. While a number of studies have shown similar results, there are others suggesting no difference in performance using the two techniques. In addition, the increased training needed for CNB and slight increase in complications may limit its use as an initial method of evaluation. However, it does suggest the need for additional study to compare the usefulness of these two diagnostic techniques. It also suggests an alternative to using molecular markers when a fine needle biopsy is non-diagnostic – although a cost comparison would need to be performed.
— Marjorie Safran, MD
ATA THYROID BROCHURE LINKS
Thyroid Nodules: https://www.thyroid.org/thyroid-nodules/
Fine Needle Aspiration Biopsy of Thyroid Nodules: https://www.thyroid.org/fna-thyroid-nodules/
ABBREVIATIONS & DEFINITIONS
Thyroid fine needle aspiration biopsy: a simple procedure that is done in the doctor’s office to determine if a thyroid nodule is benign (non-cancerous) or cancer. The doctor uses a very thin needle to withdraw cells from the thyroid nodule. Patients usually return home or to work after the biopsy without any ill effects.
Core needle biopsy (CNB): a procedure that uses a large needle and requires an experienced operator with specific training. CNB has a higher risk of complications than a fine needle biopsy, including injuries to the trachea and carotid artery.
Inadequate/Insufficient biopsy: this happens with not enough cells are obtained during the biopsy to provide a diagnosis. This occurs in 5-10% of biopsies. This often results in the need to repeat the biopsy.
Non-diagnostic thyroid biopsy: this happens when some atypical cells are found but not enough to provide a diagnosis. This occurs in 5-10% of biopsies. This often results in the need to repeat the biopsy.
Indeterminate thyroid biopsy: this happens a few atypical cells are seen but not enough to be abnormal (atypia of unknown significance (AUS) or follicular lesion of unknown significance (FLUS)) or when the diagnosis is a follicular or hurthle cell lesion. Follicular and hurthle cells are normal cells found in the thyroid. Current analysis of thyroid biopsy results cannot differentiate between follicular or hurthle cell cancer from noncancerous adenomas. This occurs in 15-20% of biopsies and often results in the need for surgery to remove the nodule.
Atypical thyroid biopsy: this happens when there are some abnormal/atypical cells in the biopsy sample but not enough to diagnose a cancer. However, because there are abnormal cells in the biopsy sample, the specimen cannot be called benign. Sometimes a repeat biopsy may be helpful but often surgery is recommended to remove the nodule.
Suspicious thyroid biopsy: this happens when there are atypical cytological features suggestive of, but not diagnostic for malignancy. Surgical removal of the nodule is required for a definitive diagnosis.
Molecular markers: genes and microRNAs that are expressed in benign or cancerous cells. Molecular markers can be used in thyroid biopsy specimens to either to diagnose cancer or to determine that the nodule is benign. The two most common molecular marker tests are the AfirmaTM Gene Expression Classifier and ThyroseqTM
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