Abstract
Purpose
Some authors have questioned the benefit of fine-needle aspiration (FNA) of thyroid nodules ≥ 4 cm. They report that the results of the FNA are not as reliable when compared to nodules < 4 cm. The aims of this study are to evaluate the accuracy and predictive values of ultrasound-guided FNA (USFNA) of thyroid nodules ≥ 4 cm and compare these findings to nodules < 4 cm.
Methods
A retrospective study of 998 patients who underwent thyroid surgery between 2006 and 2012 at the McGill University Thyroid Cancer Center was performed. USFNA and post-operative pathology diagnoses of nodules ≥ 4 cm versus those < 4 cm were compared. Pre-operative USFNA results were divided into three groups: benign, indeterminate, and malignant/suspicious for malignancy subgroups. Post-operative results were separated into benign and malignant groups.
Results
There were 225 patients with nodules ≥ 4 cm and 773 patients with nodules < 4 cm. The sensitivity, specificity, positive predictive value and negative predictive value for USFNA of nodules ≥ 4 cm were 84.62% (CI 71.91–93.10), 91.49% (CI 79.6–97.58), 91.67% (CI 80.0–97.63) and 84.31% (CI 71.4–92.95), respectively. The sensitivity, specificity, positive predictive value and negative predictive value for USFNA of nodules < 4 cm were 90.48% (CI 86.1–93.8), 85.92% (CI 75.6–93.02), 95.8% (CI 92.41–97.96) and 71.76% (CI 60.95–81.0), respectively. The difference in diagnostic accuracy of USFNA between both groups was not statistically significant ( p > 0.05).
Conclusion
This study shows that the sensitivity, specificity, positive predictive value and negative predictive value for USFNA of nodules ≥ 4 cm are similar to that of smaller nodules. It is therefore suggested that these nodules undergo USFNA.
1
Introduction
Fine-needle aspiration (FNA) is widely regarded as a first-line diagnostic tool in the management of thyroid nodules . Along with ultrasound, it forms the basis for decision making in regard to patient management. The sensitivity of FNA has been reported to range between 80% and 94% with false-negative rates of 1.9% to 12.7% . These values have varied between institutions depending on the use of ultrasound-guided versus palpation-based biopsies.
Although the necessity of FNA in the management of thyroid nodules is well established, there still exists a controversy regarding its use for larger nodules. In fact, some authors have reported that FNA of thyroid nodules ≥ 4 cm are unnecessary to dictate management . They argue that they often yield inaccurate results compared to nodules < 4 cm. Proponents of surgery also advocate that larger nodules are at higher risk of harboring malignancy, as size has previously shown to be associated with malignancy . For these reasons, they advocate for diagnostic thyroid lobectomies for nodules ≥ 4 cm without pre-operative FNA.
On the other hand, proponents of FNA of large nodules suggest that size alone should not warrant automatic surgery . Some authors advocate that the false-negative rates of FNA can be improved with the use of USFNA . Ultrasonography can in fact be used to reduce sampling errors by targeting specific areas in the nodule. Some have also shown similar predictive values when comparing USFNA of small nodules and nodules ≥ 4 cm . Thus, they recommend the use of USFNA on all nodules > 1 cm in size.
The objective of this study is to compare the accuracy and predictive values of USFNA of nodules ≥ 4 cm to smaller nodules on a large series of nearly 1000 patients.
2
Methods
This study is a retrospective review of 998 consecutive patients who underwent thyroid surgery between January 2006 and December 2012 at the McGill University Thyroid Cancer Center. Our investigation received prior approval by the hospital’s research ethics committee.
Patients were divided into two groups based on thyroid nodule size ≥ 4 cm versus < 4 cm. Pre-operative USFNA results were noted and broadly classified into three groups: benign, indeterminate, and malignant/suspicious for malignancy subgroups. Indeterminate USFNA consisted of follicular lesions/neoplasms and Hurthle cell lesions/neoplasms. The groups were then divided post-operatively into benign and malignant groups. Patients with an incidental finding of micropapillary carcinoma were categorized as benign. All USFNAs were performed by a single surgeon and done using a 20.0-gauge, 1.5-inches needle with the sample placed in CytoLyt solution (Cytyc Corporation, Marlborough, MA). An experienced thyroid cancer pathologist reviewed all histological slides. Diagnoses were made according to the World Health Organization Classification of Thyroid Tumors.
USFNA results and post-operative diagnoses were compared. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of USFNA of nodules ≥ 4 cm versus < 4 cm were calculated using the results of benign and malignant USFNA. SPSS 20.0 was used for statistical analysis using the chi-square method. p < 0.05 was considered statistically significant.
2
Methods
This study is a retrospective review of 998 consecutive patients who underwent thyroid surgery between January 2006 and December 2012 at the McGill University Thyroid Cancer Center. Our investigation received prior approval by the hospital’s research ethics committee.
Patients were divided into two groups based on thyroid nodule size ≥ 4 cm versus < 4 cm. Pre-operative USFNA results were noted and broadly classified into three groups: benign, indeterminate, and malignant/suspicious for malignancy subgroups. Indeterminate USFNA consisted of follicular lesions/neoplasms and Hurthle cell lesions/neoplasms. The groups were then divided post-operatively into benign and malignant groups. Patients with an incidental finding of micropapillary carcinoma were categorized as benign. All USFNAs were performed by a single surgeon and done using a 20.0-gauge, 1.5-inches needle with the sample placed in CytoLyt solution (Cytyc Corporation, Marlborough, MA). An experienced thyroid cancer pathologist reviewed all histological slides. Diagnoses were made according to the World Health Organization Classification of Thyroid Tumors.
USFNA results and post-operative diagnoses were compared. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of USFNA of nodules ≥ 4 cm versus < 4 cm were calculated using the results of benign and malignant USFNA. SPSS 20.0 was used for statistical analysis using the chi-square method. p < 0.05 was considered statistically significant.
3
Results
There were a total of 998 patients included in the study of which 773 had nodules < 4 cm and 225 patients had nodules ≥ 4 cm. The mean patient age was 52.25 ± 14.14 years in the < 4 cm group and 54.17 ± 15.50 years in the ≥ 4 cm group. There were 153 males (19.8%) and 620 females (80.2%) in the < 4 cm group and 38 males (16.9%) and 187 females (83.1%) in the ≥ 4 cm group. There was no statistical difference between both groups in terms of patient age and gender ( Table 1 ).
