Advancing Education, Research, and Quality of Care for the Head and Neck oncology patient.
Introduction: Diagnostic evaluation of thyroid nodules has been well studied. The Thyroid Imaging Reporting and Data System (TI-RADS) and the Bethesda system for cytopathology diagnosis are widely used and have largely standardized the diagnostic framework for thyroid cancer. The Bethesda system has categorized cytopathology results by risk of malignancy, but the ability to accurately evaluate the fine-needle aspiration (FNA) biopsy is also dependent on the quality of the tissue sample. Recent publications have suggested that there is an increased rate of false negative FNA biopsy results in patients with large nodule thyroid cancer. This study aims to investigate the accuracy of FNA biopsies in large thyroid nodules.
Study Design: Retrospective cohort
Setting: Single institution tertiary care institution
Patients: All patients who underwent a thyroid lobectomy or total thyroidectomy between April 2014 and April 2024.
Outcome Measures: Data were collected on patient demographics, family history, pre-op diagnosis, possible surgical interventions, pathology reports, time between imaging and surgical intervention, and postoperative outcomes. Categorical data were analyzed using Fischer’s exact test or ANOVA where appropriate. Continuous data were analyzed using Student’s t-test or ANOVA, where appropriate.
Results: There were 184 patients treated with a thyroidectomy. Patients were 51.9 (SD 15.7) years old, 79.9% female, and 57.1% White. 13.5% (n=24) patients had a family history of thyroid cancer. Family history of a known inherited condition was identified in one patient with a family history of multiple endocrine neoplasia type 2, but this patient received a final diagnosis of papillary thyroid carcinoma. At initial presentation, 88.3% had multinodular disease. A diagnostic ultrasound was performed in 96.7% of cases. Other imaging modalities used include 4D computed tomography (CT) neck (1.6%), Spect CT (0.5%), CT neck (26.2%), thyroid uptake scan (7.1%), and positron emission tomography with CT (2.2%). The mean diameter of the largest nodule was 2.8cm (SD 1.7cm) with a range of 0.6cm to 10.1cm. All patients underwent an FNA biopsy prior to thyroidectomy. The negative predictive value of the FNA biopsy pathologic diagnosis was 0.85 for nodules greater than 4cm in diameter. This was not different than the negative predictive value for nodules less than 4cm in diameter (0.86, p=0.73). However, the sensitivity of the FNA biopsy was lower for nodules greater than 4cm (75%) compared to nodules less than 4cm (86%, p=0.18).
Conclusions: Recent studies have suggested that large thyroid nodules have an elevated false-negative rate for thyroid cancer. The data presented in this study suggest that there is no difference in the negative predictive value of FNA biopsies of large thyroid nodules. However, there is a reduced diagnostic sensitivity that was not statistically significant. Large thyroid carcinoma nodules may have a greater risk of developing a necrotic core that can increase the risk of a sampling error, but this was not observed in this study.