Atypia and Follicular Lesions of Undetermined Significance in Subsequent Biopsy Result: What Clinicians Need to Know

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.

Interobserver variability in inconclusive diagnostic categories of thyroid fine needle aspiration cytology: An urban-based tertiary hospital experience

INTRODUCTION

Thyroid nodules are typical lesions, usually non-malignant, and surgery is unnecessary in most patients. However, distinguishing between benign and malignant is challenging. Fine needle aspiration cytology (FNAC) is considered a primary diagnostic and prognostic tool with an effective cost for evaluating thyroid enlargement. Unfortunately, using FNAC to diagnose inconclusive lesions in the category III-Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/FLUS) based on TBSRTC classification is a problematic issue. This study aimed to evaluate the interobserver variability of AUS/FLUS interpretation among pathologists.

METHODS

A retro-observational study: previous 127 AUS/FLUS cases were enrolled. Seventy-two cases met inclusion criteria and were then reclassified by different anatomical pathologists under blinded-design assignments. The concordance among pathologists and the percent alteration of the risk of malignancy (ROM) were compared to the original reports and histological diagnosis.

RESULTS

About 72 % of AUS/FLUS cases were changed after the reclassification. Approximately 46 % were changed to benign while 12.5 % were reclassified as carcinoma. Moreover, 30 % of those original AUS/FLUS were histologically diagnosed as malignant or carcinoma lesions. The concordances among consensus diagnosis and results from each pathologist are acceptable, Kappa(s) were 0.674 to 0.898 (p < 0.001) and Spearman correlations were 0.820 to 0.957 (p < 0.0001).

CONCLUSION

There are substantial interobserver differences and changes in cytological diagnosis when re-evaluation is performed by multiple pathologists using TBSRTC. A second or third opinion should be sought routinely to establish a consensus diagnosis as a supplement to the initial diagnosis of AUS/FLUS. The reclassification reduces medical expenses and the rate of unnecessary surgery, especially in patients with cytologically confirmed benign thyroid nodules. Preoperative molecular evaluation is a promising method for assisting in the diagnosis of thyroid nodules, but additional research is necessary.

Optimization of the Management of Category III Thyroid Nodules Using Repeat FNA and TIRADS

The aim of the study was to examine the benefits of the joint use of repeat FNA (rFNA) and EU-TIRADS in category III nodules in relation to the kind of atypia: nuclear vs. architectural (denoted by AUS and FLUS respectively). The study included 127 AUS and 1739 FLUS nodules with a known category of EU-TIRADS. Repeat FNA was performed in 82 AUS and 934 FLUS nodules of which 57 and 515 were excised, respectively. AUS nodules had higher malignancy risk than FLUS nodules. EU-TIRADS showed higher accuracy for AUS nodules, the opposite to rFNA, that had higher accuracy for FLUS nodules. The combined criterion for AUS nodules (at least rFNA-V or EU-TIRADS-4) maximized sensitivity (92.3%) with acceptable specificity (70.0%); OR: 28.0. In the case of FLUS nodules, the combined criterion (rFNA-V or EU-TIRADS-5) maximized specificity (95.2%) with 57.7% sensitivity and a low percentage (13.9%) of positive nodules, OR: 27.0. In both types of nodules, the low risk category in EU-TIRADS and benign result of rFNA excluded cancer. Concluding, category III nodules with and without nuclear atypia differ in their risk of malignancy and, consequently, diagnostic criteria adopted for the evaluation of these nodules with rFNA and EU-TIRADS should be specific to AUS and FLUS nodules.

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.

Hashimoto's Thyroiditis Does Not Influence the Malignancy Risk in Nodules of Category III in the Bethesda System

The aim of this study was to evaluate the risk of malignancy (RoM) in category III thyroid nodules of the Bethesda system in patients with and without Hashimoto thyroiditis (HT) and to analyze whether obtaining category III with a repeat FNA (rFNA) increases RoM. The study included 563 HT and 1250 non-HT patients; rFNA was performed in 349 and 575 patients, and surgical treatment in 160 and 390, respectively. There was no difference in RoM between HT and non-HT patients in the whole examined population (lower limit of RoM), nor in operated patients (upper limit of RoM), HT: 5.0−17.5%, non-HT: 4.7−15.1%. RoM in patients with AUS nodules (with nuclear atypia) was similar in both groups (HT: 21.7−40.0%, non-HT: 16.9−41.4%), as it was in patients with FLUS nodules (with architectural atypia) (HT: 3.5−13.3%, non-HT: 4.0−13.0%). In patients from both groups together, with category III diagnosed twice and AUS identified at least once, RoM was 16.7−50.0% and it was higher than that in patients with FLUS nodule diagnosed twice: 3.2−13.0% (p < 0.005). Concluding, RoM in category III nodules is not affected by the presence of HT. Subcategorization of category III nodules (FLUS vs. AUS) may provide guidance toward further follow-up or surgery in both groups.