The Usefulness of Core Needle Biopsy in the

• Thyroid nodules are common in clinical practice, and although more than 90% of these are benign:
  • Thyroid cancer remains the most frequent endocrine cancer
• Fine-needle aspiration biopsy (FNAB):
  • Is still considered the most critical tool in stratifying the risk of malignancy when evaluating thyroid nodules:
    • It is simple, effective, low-cost, and safe:
      • However, one of the most critical limitations of FNAB is the relatively high frequency of:
        • Unsatisfactory (non-diagnostic) samples or
        • Cytologically indeterminate results such as:
          • Atypia or follicular lesion of undetermined significance
      • These limitations have led some to consider other diagnostic tools, including:
        • Core-needle biopsy (CNB)
      • Even though CNB is considered controversial, many publications, especially from Asia:
        • Have reported it as an effective and safe sampling method for the diagnostic evaluation of thyroid nodules:
          • Especially for nodules with previously inadequate or indeterminate FNAB results
  • The current study, Clin Thyroidol 2021;33:487–489:
    • Aimed to compare the performance of CNB versus FNA:
      • As the first option in the evaluation of thyroid nodules
  • Methods:
    • This was a multicenter retrospective study that collected data regarding FNAB and CNB results of thyroid nodules from three institutions
    • In one institution, 705 patients underwent CNB by a single operator as the first evaluation of thyroid nodules that were given a high estimated likelihood of obtaining nondiagnostic cytologic results with FNAB:
      • Thyroid nodules that were heavily calcified
      • Were predominantly cystic
      • Were > 5 mm with suspicious ultrasound features
      • Had sonographic features suspicious for follicular neoplasms
      • Were candidates for radiofrequency ablation therapy
    • In the other two centers, FNAB was the initial diagnostic option in 583 patients
    • Ultrasound features of the thyroid nodules were categorized according to the Korean Thyroid Imaging Reporting and Data System (K-TIRADS)
    • The diagnosis of malignancy was determined by CNB or FNAB cytology or by histopathologic findings from surgical resection
    • The Bethesda System for Reporting Thyroid Cytopathology was used to categorize the CNB and FNAB results
    • The diagnosis of benign nodules was confirmed on at least two benign results via CNB or FNAB or on one benign report on CNB or FNAB in the absence of indeterminate or malignant results in the initial or repeat biopsy or in the final histologic surgical pathology report
    • The diagnostic performance of each aspiration method was evaluated based on sensitivity, specificity, accuracy, positive predictive value, negative predictive value (NPV), and area under the receiver-operating-characteristic (ROC) curve (AUC) values
  • Results:
    • The frequency of nondiagnostic, atypia/follicular lesion of undetermined significance (AUS/FLUS), and suspicious for malignancy lesions:
      • Were all significantly lower in the CNB group than in the FNAB group
    • The CNB group also showed a:
      • Significantly lower inconclusive diagnostic rate than the FNAB group
    • The frequencies of suspicious follicular neoplasms and malignant cytologies were:
      • Substantially higher in the CNB group than in the FNAB group
    • The sensitivity, NPV, and accuracy were significantly higher in the CNB group than in the FNAB group
    • On ROC analysis, the AUCs of CNB were markedly higher than those for FNAB
    • The FNAB group included a small number of false-negative FNAB results (two K-TIRADS 5 nodules: 2 of 244 nodules [0.8%]) and false-positive FNAB results (one K-TIRADS 3 or 4 nodule: 1 of 141 nodules [0.7%])
    • There were no false-negative or false-positive results in the CNB group
    • When comparing the diagnostic performance of CNB and FNAB according to ultrasound features:
      • The sensitivity, NPV, and accuracy of CNB were all significantly higher than those of the FNAB group
    • There were no complications in the FNAB group
    • In the CNB group,:
      • Five patients (0.7%) developed perithyroidal hemorrhage or intrathyroidal hemorrhage that was resolved by manual compression
• Conclusions:
  • This study showed that CNB was superior to FNAB as the initial diagnostic aspiration tool for evaluating thyroid nodules, regardless of the ultrasound findings
  • The findings suggest that CNB is a reasonable option, as compared with FNAB, for the initial assessment of thyroid nodule cytology

• FNAB is considered the gold standard in the stratification of malignancy risks when evaluaing thyroid nodules:
  • It is generally cost-effective, simple, safe, and accurate:
    • However, it has some limitations, including a:
      • Significant inconclusive rate
      • Some false-negative results
      • A relatively high incidence of nondiagnostic or indeterminate results:
        • Categories I, III, and IV of the Bethesda System for Reporting Thyroid Cytopathology
• Since 2011, some papers from Asia and South Korea in particular have proposed using CNB as an efficient option for the evaluation of thyroid nodules and that in many ways it may be even better than FNAB
• Other studies have also shown no differences in diagnostic performance between these two techniques:
  • However, using CNB as a standard initial tool for obtaining thyroid nodule cytology faces some problems:
    • CNB is more invasive than FNAB
    • It requires specific training
    • Rare complications have been reported, including:
      • Injury to the trachea and carotid artery
    • In order to avoid such complications, an experienced operator is mandatory
  • Some recent guidelines have proposed the use of CNB as a complementary exam in select cases with non-diagnostic or indeterminate results obtained by FNAB, which is very reasonable
  • The size of the nodule, ultrasound features, and cytologic findings of the FNAB:
    • Are all factors that showed consider when deciding to perform CNB instead of repeating FNAB
  • In addition, for some patients, CNB may avert the need to perform molecular tests
  • Over time, CNB has been increasingly accepted as an appropriate initial exam; it can yield good results when indicated in select patients and when performed by a trained professional

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