Investigation of pre-operative demographic, biochemical, sonographic and cytopathological findings in low-risk thyroid neoplasms

OBJECTIVE

The present article analyses pre-operative demographic, biochemical, sonographic and histopathological characteristics of low-risk thyroid neoplasms (LRTNs), with a focus on four subgroups, "well-differentiated carcinoma-not otherwise specified" (WDC-NOS), "non-invasive follicular thyroid neoplasm with papillary like nuclear features" (NIFTP), "well-differentiated tumours of uncertain malignant potential" (WDT-UMP) and "follicular tumour of uncertain malignant potential" (FT-UMP).

METHODS

The study retrospectively analyzed the histopathology of 2453 malignant thyroids and the final analyses included 99 cases diagnosed with LRTNs. The demographic and clinical features, pre-operative thyroid function, ultrasonography results, cytopathology results, histopathology results and prognostic classifications were assessed.

RESULTS

The groups were similar demographic characteristics and the majority of clinical data, including comorbidities, thyroid function tests, thyroid cancer/neck radiotherapy history. NIFTPs represented 69.7% of all LRTNs. All (100%) WDT-UMPs had solitary nodules. Index nodule volume differed among the groups (p = .036), it was the lowest in WDC-NOS [0.68 (0.63-0.72 cc)] and highest in FT-UMP [12.6 (0.5-64 cc)]. Echogenicity findings were similar. Index nodule TIRADS demonstrated a significant difference (p = .021) but index nodule halo sign and BETHESDA scores were similar in all groups. The diameter, localisation and multicentric structure of LRTNs were again similar for all groups. Finally, prognostic scores suggested similar outcomes in all groups.

CONCLUSION

The majority of LRTNs were NIFTPs in our population and all WDT-UMPs were solitary lesions. Index nodule volume was the most essential discriminating sonographic finding but further research must be performed before discriminatory potential can be described.

Cytological features and nuclear scores: Diagnostic tools in preoperative fine needle aspiration of indeterminate thyroid nodules with RAS or BRAF K601E mutations?

INTRODUCTION

The cytological diagnosis of follicular-patterned thyroid lesions is challenging, especially since the World Health Organisation classification has recognised non-invasive follicular thyroid neoplasm with papillary-like features. These entities are often classified as indeterminate on cytology. Molecular testing has been proposed to help classify indeterminate nodules. RAS and K601E BRAF mutations are mostly encountered in follicular-patterned lesions, but their diagnostic value is not well established. Nuclear scores have also been proposed to help classify indeterminate lesions.

OBJECTIVE

To investigate the correlation between cytological features and histology and to assess nuclear scores in a series of indeterminate RAS or BRAF K601E positive thyroid nodules.

METHODS

The cytological parameters of 69 indeterminate RAS or BRAF K601E-positive thyroid nodules were evaluated. The Strickland and Maletta scores and a new nuclear score were assessed. Diagnosis of malignant, benign or indolent neoplasms was confirmed in each case by histology. Malignant and indolent nodules were considered surgical nodules, and adenomas non-surgical nodule.

RESULTS

Surgical nodules were associated with the presence of ground glass nuclei (P = .001), grooves (P < .001) or irregular nuclear membranes (P = .01) on cytology. Nuclear scores were more often ≥2 in surgical nodules compared to benign ones (P < .001), with high sensitivity, but a low negative predictive value.

CONCLUSIONS

Analysis of nuclear features is useful to distinguish non-surgical from surgical nodules in indeterminate FNAs. Although nuclear scores are not ideal rule-out tests for indeterminate RAS or BRAF K601E positive nodules, they seem useful to screen non-molecular tested or non-mutated indeterminate FNAs. This work shows that meticulous analysis of nuclear features on cytological specimens can be useful to distinguish non-surgical nodules (adenoma) from surgical nodules in indeterminate FNAs. Although nuclear scores are not rule-out tests for indeterminate RAS or BRAF K601E positive nodules, they are useful in screening non-molecular tested or non-mutated indeterminate FNAs for surgery.

Cytomorphology of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features and the Impact of New Nomenclature on Molecular Testing

The re-naming of noninvasive follicular variant papillary thyroid cancer to the apparently non-malignant, noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) impacts the prevalence of malignancy rates, thereby affecting mutation frequency in papillary thyroid cancer. Preoperative assessment of such nodules could affect management in the future. The original publications following the designation of the new nomenclature have been extensively reviewed. With the adoption of NIFTP terminology, a reduction in the follicular variant of papillary thyroid cancer (FVPTC) prevalence is anticipated, as is a modest reduction of papillary thyroid cancer (PTC) prevalence that would be distributed mainly across indeterminate thyroid nodules. Identifying NIFTP preoperatively remains challenging. RAS mutations are predominant but the presence of BRAF V600E mutation has been observed and could indicate inclusion of the classical PTC. The histological diagnosis of NIFTP to designate low-risk encapsulated follicular variant papillary thyroid cancers (EFVPTCs) would impact malignancy rates, thereby altering the mutation prevalence. The histopathologic criteria have recently been refined with an exclusion of well-formed papillae. The preoperative identification of NIFTP using cytomorphology and gene testing remains challenging.

Preoperative Molecular Markers in Thyroid Nodules

The need for distinguishing benign from malignant thyroid nodules has led to the pursuit of differentiating molecular markers. The most common molecular tests in clinical use are Afirma^® Gene Expression Classifier (GEC) and Thyroseq^® V2. Despite the rapidly developing field of molecular markers, several limitations exist. These challenges include the recent introduction of the histopathological diagnosis "Non-Invasive Follicular Thyroid neoplasm with Papillary-like nuclear features", the correlation of genetic mutations within both benign and malignant pathologic diagnoses, the lack of follow-up of molecular marker negative nodules, and the cost-effectiveness of molecular markers. In this manuscript, we review the current published literature surrounding the diagnostic value of Afirma^® GEC and Thyroseq^® V2. Among Afirma^® GEC studies, sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) ranged from 75 to 100%, 5 to 53%, 13 to 100%, and 20 to 100%, respectively. Among Thyroseq^® V2 studies, Se, Sp, PPV, and NPV ranged from 40 to 100%, 56 to 93%, 13 to 90%, and 48 to 97%, respectively. We also discuss current challenges to Afirma^® GEC and Thyroseq^® V2 utility and clinical application, and preview the future directions of these rapidly developing technologies.