The Prediction of Malignancy Risk in Thyroid Nodules Classified as Bethesda System Category III (AUS/FLUS) and the Role of Ultrasound Finding for Prediction of Malignancy Risk

Rates and Predictors of Malignancy in Bethesda III and IV Thyroid Nodules: A Prospective Study

AIM

Thyroid nodules, based on high-resolution ultrasonography (HRUS), are among the most common endocrine abnormalities that affect the general population because of their high estimated prevalence rates. Fine needle aspiration cytology (FNAC) is a safe, cost-effective modality to differentiate between benign and malignant thyroid nodules based on the Bethesda System for Reporting Thyroid Cytopathology (BSRTC), thus avoiding unnecessary surgery. However, categories III and IV of BSRTC remain a controversial issue in clinical practice, encompassing a wide range of risks of malignancy. Hence, our study aimed to assess the malignancy rates of thyroid nodules classified as Bethesda III and IV categories as evidenced by post-thyroidectomy histopathology; study the association between the American College of Radiologists Thyroid Image Reporting and Data System (ACR-TIRADS) score of these two categories and the postoperative histopathological analysis; and study the predictors of malignancy in these two categories.

MATERIALS AND METHODS

A prospective study was conducted on 242 patients who underwent FNAC throughout the study from December 2022 to August 2023. All patients who performed FNAC were primarily subjected to history taking, clinical examination, thyroid-stimulating hormone (TSH), thyroid autoantibodies (antithyroglobulin (anti-TG) and thyroid peroxidase antibodies (TPO Abs)), and HRUS with a further categorization of thyroid nodules according to the ACR-TIRADS scoring system. The cytological aspirates were categorized according to the BSRTC. Patients with Bethesda III and IV categories were resorted to surgery according to clinical factors, sonographic features, and patients' preferences.

RESULTS

A total of 17 cases with Bethesda III and 65 patients with Bethesda IV were included. Seventy-one out of 82 patients (86.6%) underwent surgical intervention. The proportions of malignant nodules classified as TIRADS-2, TIRADS-3, TIRADS-4, and TIRADS-5 scores were 0.0, 4.5 (n=1/22), 22.7 (n=5/22), and 72.7% (n=16/22), respectively. The rate of malignancy was 18.2% (n=2/11) among class III and 33.3% (n=20/60) among class IV-categorized Bethesda thyroid nodules. In univariate logistic regression analysis, age ≥ 40 years, body mass index ≥ 30 kg/m², higher TSH, positive anti-TG antibodies, radiation exposure, irregular borders, marked hypoechogenicity, ill-defined margins, microcalcifications, solid consistency, taller than wide growth, solitary nodule, and nodule size > 2 cm, and suspicious lymph nodes were associated with higher malignancy risk. In multivariate regression analysis, positive anti-TG Abs, radiation exposure, irregular borders, taller-than-wide growth, hypoechogenicity, calcifications, and solid consistency remain to be independent predictors of malignancy.

CONCLUSION

The malignancy rates of Bethesda class III and IV nodules in this study met the estimated malignancy risk proposed by BSRTC. TIRADS scores 4 and 5 confer a higher risk of malignancy in Bethesda III and IV thyroid nodules. Positive thyroglobulin antibodies and radiation exposure are independent factors of malignancy in Bethesda III and IV nodules. Moreover, ultrasound features, including irregular borders, taller-than-wider growth, hypoechogenicity, calcifications, and solid consistency, are associated with increased malignancy risk and should be considered in the surgical selection of patients.

Prevalence of malignancy in thyroid nodules with AUS cytopathology: A retrospective cross-sectional study

Background

Category III (AUS; Atypia of Undetermined Significance) of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) was established to describe thyroid nodule features that are neither benign nor cancerous.

Objectives

This study aims to evaluate the rate of thyroid malignancy in patients diagnosed with AUS at the Armed Forces Hospital Southern Region (AFHSR), Saudi Arabia.

Method

The patients (508) diagnosed with AUS in their thyroid nodules underwent fine-needle aspiration cytology (FNAC). Data were collected through a chart-based approach, reviewing patients' medical records and relevant information.

Results

Among the cases, the majority were females (84.6%). Among the different age groups, individuals between 40 and 50 years had the highest prevalence of thyroid nodules (32.5%). Approximately 27% of patients exhibited tumor sizes larger than 4 cm. FNAC results revealed 16.5% benign, 26% AUS, and 22.4% follicular neoplasm cases. Histopathology indicated 54.1% of benign and 37.2% of malignant cases. Papillary carcinoma accounts for 80.4% of all malignant cases. A significant correlation was observed between FNAC and postoperative histopathology (P value < 0.05). Hypoechoic nodules exhibited 33.9% of malignant cases, and calcification was observed in 25% of the cases. A significant association was found between malignancy and echogenicity and between malignancy and calcification (P value = 0.003 and 0.001, respectively).

Conclusion

The findings of this study identify malignancy in thyroid nodules with AUS cytopathology, particularly in the Southern region of Saudi Arabia. The correlation between pre-surgery FNAC and postoperative histopathology supports FNAC's diagnostic value. Additionally, echogenicity and calcification can potentially contribute to predicting nodule malignancy.

Ultrasonographic predictors of thyroid cancer in Bethesda III and IV thyroid nodules

Background

Bethesda III and IV thyroid nodules continue to be difficult to manage. Although molecular testing may assist in decision-making, it is expensive, not widely available, and not without pitfalls. The objective of this study is to assess whether certain thyroid ultrasonographic features may predict the risk of thyroid cancer in patients with Bethesda III and IV thyroid nodules and be used as additional decision-making tools to complement cytopathological results in deciding on diagnostic thyroidectomy.

Methods

We retrospectively evaluated the ultrasonographic features of Bethesda categories III and IV thyroid nodules in patients who underwent subsequent thyroidectomy. We used the final histopathological examination of the surgical specimens as the gold-standard test and analyzed individual preoperative ultrasonographic features as predictors of malignancy.

Results

Of the 278 patients who were diagnosed with Bethesda III and IV thyroid nodules on fine needle aspiration cytology (FNAC), 111 (39.9%) had thyroid cancer, and 167 (59.9%) exhibited benign nodules. The malignancy rate was higher in patients with Bethesda IV nodules (28/50, 56%) than those with Bethesda III nodules (83/228, 36.4%; p=0.016). In univariate analysis, hypoechogenicity (55.6% in malignant vs. 35.3% in benign, p=0.006) and calcifications (54.5 in malignant vs. 35.4% in benign, p=0.008) were significantly different between the benign and malignant pathology groups, whereas the size of the dominant nodule, number of nodules, irregular borders, taller-than-wide shape, and the presence of lymph nodes were comparable between the two groups. These two ultrasonographic features (hypoechogenicity and calcifications) remained significantly associated with the risk of malignancy in multivariate logistic regression analysis (for hypoechogenicity, p=0.014, odds ratio: 2.1, 95% CI:1.0-3.7 and for calcifications, p=0.019, odds ratio: 1.98, 95% CI:1.12-3.50). The sensitivity, specificity, positive and negative predictive values, and accuracy were 31.5%, 83%, 55.6%,64.7%, and 62.6%, for hypoechogenicity, respectively and 32.4%, 82%, 54.5%, 67.8%, and 62%, for calcification, respectively.

Conclusions

Hypoechogenicity and calcifications in Bethesda III and IV thyroid nodules are strong predictors of thyroid cancer and associated with a two-fold increased risk of malignancy.

The Role of "Critical" Ultrasound Reassessment in the Decision-Making of Bethesda III Thyroid Nodules

Background and Objectives: Bethesda III (BIII) thyroid nodules have an expected malignancy rate of 5-15%. Our purpose was to assess which US criteria are most associated with cancer risk, and the value of critical ultrasound (US) reassessment. Methods: From 2018 to 2022, 298 BIII nodules were enrolled for thyroidectomy (79 malignancies). We evaluated ultrasonographic data: hechogenicity, intralesional vascularization, spiculated margins, micro-calcifications, "taller than wide" shape, extra-thyroidal growth, size increase, as well as their association with histology. We also evaluated if the ultrasound reassessment modified the strategy. Results: Spiculated margins and microcalcification were significantly correlated with malignancy risk. Spiculated margins showed a specificity of 0.95 IC95% (0.93-0.98); sensitivity 0.70 IC95% (0.59-0.80). Microcalcifications showed a sensitivity of 0.87 CI95% (0.80-0.94); specificity 0.75 CI95% (0.72-0.83). The presence of these signs readdressed the strategy in 76/79 cases Then, the indication for surgery was appropriate in 75% of cases. Conclusions: Microcalcifications and spiculated margins should be routinely sought during a final ultrasound reassessment in BIII nodules. These signs allowed for a modification of the strategy in favor of surgery in 96% of the cases that were not otherwise referred to surgery. The importance of integrating ultrasound and cytology in the evaluation of BIII thyroid nodules is confirmed. Reassessment with ultrasound of BIII nodules allowed for a redirection of the surgical choice.

Current controversies in the management of patients with indeterminate thyroid nodules

The management of cytologically indeterminate thyroid nodules remains debatable as their malignancy is difficult to establish. Most nodules have benign postoperative histology, but an accurate assessment of their proclivity for malignant transformation is crucial. Numerous studies have investigated the effects of various tools, including clinical, radiological, and cytological features, as well as biochemical and molecular markers, on the management of these heterogeneous nodules. Collectively, strategies aim to treat malignant nodules and avoid unnecessary surgery for asymptomatic benign nodules. Currently, no clear guidelines for the optimal management of cytologically indeterminate thyroid nodules exist to determine whether a conservative approach with long-term observation or surgical intervention should be selected. Thus, personalized approaches have been recommended. Large-scale multicenter prospective studies are needed to elucidate controversial issues. As this topic has not been comprehensively covered based on publications from the Gulf region, this review aims to shed light on remaining controversies.

Preoperative evaluation of thyroid nodules - Diagnosis and management strategies

Thyroid cancer is the most common endocrine malignancy, with increasing incidence over the past few decades. Fine needle aspiration (FNA) biopsy is the gold standard for preoperative diagnosis of thyroid malignancies. Nevertheless, this method renders indeterminate results in up to 30% of the cases. Therefore, these patients are often referred to unnecessary surgery to establish the diagnosis. To improve the accuracy of preoperative diagnosis, several other ways, such as ultrasonography, elastography, immunohistochemical analysis, genetic testing, and core needle biopsy, have been developed and can be used either in association with or as an alternative to FNA. This review aims to evaluate all these diagnostic tools to determine the most appropriate way of managing thyroid nodules and subsequently improve the selection of cases referred to surgery.

Assessment of Preoperative TSH Serum Level and Thyroid Cancer Occurrence in Patients with AUS/FLUS Thyroid Nodule Diagnosis

Thyroid-stimulating hormone (TSH) is a growth factor associated with the initiation and progression of well-differentiated thyroid cancer (WDTC). Atypia of undetermined significance and follicular lesion of undetermined significance (AUS/FLUS) are the most uncertain cytological diagnoses of thyroid nodules. The aim of the study was to determine the association of histopathological diagnosis with preoperative serum TSH levels in patients with AUS/FLUS thyroid nodule diagnosis. Among 5028 individuals with thyroid nodules, 342 (6.8%) with AUS/FLUS diagnoses were analyzed. The frequency of all histopathology diagnoses was assessed for associations with preoperative serum TSH levels. The median TSH concentration was significantly higher in patients with AUS/FLUS diagnosis and histopathology of WDTC than in patients with the same cytology result and histopathology of a benign tumor (p < 0.0001). The diagnostic potential of serum TSH level was determined to evaluate risk of malignancy in patients with thyroid nodules classified into the Bethesda III category. ROC analysis showed the TSH concentration at a cutoff point of 2.5 mIU/L to be an acceptable prognostic factor for WDTC. For this optimal cutoff point, the AUC was 0.877, the sensitivity was 0.830, and the specificity was 0.902. Preoperative serum TSH levels in patients with AUS/FLUS thyroid tumor diagnosis should be taken into consideration in the decision-making process and clinical management.

Systematic review and meta-analysis: diagnostic value of different ultrasound for benign and malignant thyroid nodules

BACKGROUND

Conventional ultrasound and contrast-enhanced ultrasound (CEUS) are commonly used in the diagnosis of benign and malignant thyroid nodules. However, the value of the two methods in the diagnosis of benign and malignant thyroid nodules remains controversial.

METHODS

PubMed, Medline, EBSCO, Science Direct, Cochrane Library, China National Knowledge Infrastructure (CNKI) database and manual journal retrieval were searched from January 2000 to January 2022, to include research on conventional ultrasound or CEUS in the diagnosis of benign and malignant thyroid nodule related clinical studies. Meta-analysis was conducted using RevMan5.3 and Stata Corp to analyze the sensitivity and specificity of conventional ultrasound and CEUS in the diagnosis of benign and malignant thyroid nodules with 95% confidence interval (CI) as indicators. Heterogeneity of the results was evaluated by Q test and I2 in RevMan5.3. Deek's method was used to evaluate publication bias.

RESULTS

A total of 1,378 nodules were included in 11 literatures, including 535 malignant thyroid nodules and 843 benign thyroid nodules. Heterogeneity tests conducted for CEUS diagnostic sensitivity of the 6 included literatures indicated that there was no heterogeneity among the study groups [Q=2.05, degree of freedom (df) =5.00, I2=0.00%, P=0.84]. The combined sensitivity was 0.87, with 95% confidence interval (CI): 0.82 to 0.90. Heterogeneity tests on the diagnostic specificity of CEUS of the six included literatures suggested that there was heterogeneity among the different study groups (Q=14.27, df =5.00, I2=64.96%, P=0.01). The combined specificity was 0.84 (95% CI: 0.78 to 0.89). Heterogeneity tests performed on the sensitivity of five conventional ultrasound diagnosis articles revealed that there was heterogeneity among different study groups (Q=13.62, df =4.00, I2=70.64%, P=0.01). The combined sensitivity was 0.86 (95% CI: 0.78 to 0.92). Heterogeneity tests on the specificity of conventional ultrasound diagnosis in five included literatures indicated that there was heterogeneity among different study groups (Q=16.94, df =4.00, I2=76.39%, P=0.00). The combined specificity was 0.84 (95% CI: 0.75 to 0.90). There was no bias in the included literature.

DISCUSSION

The sensitivity of CEUS in the diagnosis of benign and malignant thyroid nodules was slightly higher than that of conventional ultrasound, which provides a reference for the clinical diagnosis of benign and malignant thyroid nodules.

Predictors of Malignancy in Thyroid Nodules Classified as Bethesda Category III

OBJECTIVE

To determine predictors of malignancy in surgically treated Bethesda category III nodules.

METHODS

Patients with surgically treated thyroid nodules classified as Bethesda category III were retrospectively enrolled. The association between clinical/sonographic features and postoperative pathology was evaluated using univariate and multivariate analyses.

RESULTS

A total of 188 nodules from 184 patients were included. The overall malignancy rate was 54.3%. In univariate analysis, male sex, aspect ratio >1, microcalcification, unclear boundary, BRAFV600E mutation, and nuclear atypia were significantly associated with malignant disease in Bethesda category III nodules. Multivariate analysis confirmed that male sex, aspect ratio >1, microcalcification, and BRAFV600E mutation were independent predictors of malignant disease.

CONCLUSIONS

Malignant disease was common in Bethesda category III nodules, and surgical treatment was strongly indicated in the presence of male sex, aspect ratio>1, microcalcification, and BRAFV600E mutation.