Active Surveillance for Papillary Thyroid Microcarcinoma: Challenges and Prospects

PESI-MS combined with AI to build a prediction model for lymph node metastasis of papillary thyroid cancer

OBJECTIVE

Construct a prediction model for lymph node metastasis (LNM) in papillary thyroid carcinoma (PTC) using Probe Electrospray Ionization Mass Spectrometry (PESI - MS) combined with artificial intelligence (AI), to assist in the preoperative prediction of lymph node metastasis in thyroid carcinoma by intraoperative frozen pathology.

METHODS

A total of 78 fresh tissue samples of PTC and their adjacent normal tissues were collected. After proper processing, these samples were subjected to detection and analysis using PESI - MS. Subsequently, a classification prediction model was established based on the mass spectrometry test results integrated with AI algorithms. Support vector machine (SVM), random forest (RF), multi - layer perceptron (MLP), and Gradient boosting classifier (GBC) were employed for model building. Employing Support Vector Machine (SVM), Random Forest (RF), and Multilayer Perceptron (MLP) to conduct a single-blinded test on 10 independent PTC samples with unknown lymph node metastasis status.

RESULTS

The SVM, and MLP algorithms achieved an accuracy of 100 % in differentiating PTC with or without LNM, while the RF and GBC algorithm reached an accuracy of 92 %. All four algorithms demonstrated an accuracy of 100 % in distinguishing PTC from adjacent normal tissues.

CONCLUSION

The combination of PESI - MS and AI exhibits high accuracy in predicting LNM in PTC and performs remarkably well in the rapid diagnosis of PTC. This approach can effectively assist in the rapid diagnosis of intraoperative pathology, assist in determining the surgical scope of thyroid lymph node dissection, and offer more precise treatment for patients.

Enhancement on CT for preoperative diagnosis of metastatic lymph nodes in thyroid cancer: a comparison across experience levels

OBJECTIVES

To investigate the diagnostic performance and interobserver agreement of quantitative CT parameters indicating strong lymph node (LN) enhancement in differentiated thyroid cancer (DTC), comparing them with qualitative analysis by radiologists of varying experience.

MATERIALS AND METHODS

This study included 463 LNs from 399 patients with DTC. Three radiologists independently analyzed strong LN enhancement on CT. Qualitative analysis of strong enhancement was defined as LN cortex showing greater enhancement than adjacent muscles on the arterial phase. Quantitative analysis included the mean attenuation value (MAV) of LN on arterial phase (LNA) and venous phase (LNV), LNA normalized to the common carotid artery (NAVCCA), internal jugular vein (NAVIJV), and sternocleidomastoid muscle (NAVSCM), attenuation difference [AD; (LNA - MAVSCM)], and relative washout ratio [((LNA - LNV)/LNA) × 100]. The interobserver agreement and diagnostic performance of the quantitative and qualitative analyses were evaluated.

RESULTS

Interobserver agreement was excellent for all quantitative CT parameters (ICC, 0.83-0.94) and substantial for qualitative assessment (κ = 0.61). All CT parameters except for LNV showed good diagnostic performance for metastatic LNs (AUC, 0.81-0.85). NAVCCA (0.85, 95% CI: 0.8-0.9) and AD (0.85, 95% CI: 0.81-0.89) had the highest AUCs. All quantitative parameters except for NAVIJV had significantly higher AUCs than qualitative assessments by inexperienced radiologists, with no significant difference from assessments by an experienced radiologist.

CONCLUSION

Quantitative assessment of LN enhancement on arterial phase CT showed higher interobserver agreement and AUC values than qualitative analysis by inexperienced radiologists, supporting the need for a standardized quantitative CT parameter-based model for determining strong LN enhancement.

CLINICAL RELEVANCE STATEMENT

When assessing strong LN enhancement in DTC, quantitative CT parameters indicating strong enhancement can improve interobserver agreement, regardless of experience level. Therefore, the development of a standardized diagnostic model based on quantitative CT parameters might be necessary.

KEY POINTS

Accurate preoperative assessment of LN metastasis in thyroid cancer is crucial. Quantitative CT parameters indicating strong LN enhancement demonstrated excellent interobserver agreement and good diagnostic performance. Quantitative assessment of contrast enhancement offers a more objective model for the identification of metastatic LNs.

The survival after thyroidectomy versus lobectomy in multifocal papillary thyroid microcarcinoma patients

BACKGROUND

The extent of thyroid surgery for multifocal papillary thyroid microcarcinoma (PTMC) remains controversial. Studies on the optimal surgical approach for a multifocal PTMC are scarce. This study aimed to compare the effectiveness of thyroidectomy and lobectomy for the treatment of multifocal PTMC.

METHODS

A population-based retrospective cohort of patients with multifocal PTMC was analyzed using the Surveillance, Epidemiology, and End Results (SEER) database between 2004 and 2017, and divided into two groups (thyroidectomy, lobectomy) based on the surgical approach. The clinicopathologic features and survival outcomes were compared between the two groups. Cox proportional hazards regression analysis to explore prognostic factors of survival. Propensity score matching (PSM) was used to balance covariates.

RESULTS

Overall, a total of 9387 multifocal PTMC patients were included in the study. Among them, 8,107 (86.36%) patients received thyroidectomy, and 1280 (13.64%) patients underwent lobectomy. Compared to patients in the thyroidectomy group, patients in the lobectomy group were diagnosed with older age (50.47 years vs. 49.32 years, p = 0.003), a higher proportion of males (20.47% vs. 14.99%, p < 0.001), larger tumors (6.22 mm vs. 4.97 mm, p < 0.001), and more frequently underwent radiotherapy (35.40% vs. 10.16%, p < 0.001). Multivariate Cox regression analysis revealed that age was the only independent prognostic factor for thyroid cancer-specific survival (TCSS), and the determinants of overall survival (OS) were age and gender. Unadjusted survival analysis revealed no difference between the two treatment groups in TCSS (p = 0.598) and OS (p = 0.126). After 1:1 Propensity Score Matching (PSM), there was still no difference in TCSS (p = 0.368) or OS (p = 0.388). The stratified analysis revealed that for patients aged under or above 55, thyroidectomy was not associated with superior BCSS or OS (p > 0.05).

CONCLUSIONS

Thyroidectomy was not associated with improved survival compared to thyroid lobectomy for patients with multifocal PTMC.

Pathomics and single-cell analysis of papillary thyroid carcinoma reveal the pro-metastatic influence of cancer-associated fibroblasts

BACKGROUND

Papillary thyroid carcinoma (PTC) is globally prevalent and associated with an increased risk of lymph node metastasis (LNM). The role of cancer-associated fibroblasts (CAFs) in PTC remains unclear.

METHODS

We collected postoperative pathological hematoxylin-eosin (HE) slides from 984 included patients with PTC to analyze the density of CAF infiltration at the invasive front of the tumor using QuPath software. The relationship between CAF density and LNM was assessed. Single-cell RNA sequencing (scRNA-seq) data from GSE193581 and GSE184362 datasets were integrated to analyze CAF infiltration in PTC. A comprehensive suite of in vitro experiments, encompassing EdU labeling, wound scratch assays, Transwell assays, and flow cytometry, were conducted to elucidate the regulatory role of CD36+CAF in two PTC cell lines, TPC1 and K1.

RESULTS

A significant correlation was observed between high fibrosis density at the invasive front of the tumor and LNM. Analysis of scRNA-seq data revealed metastasis-associated myoCAFs with robust intercellular interactions. A diagnostic model based on metastasis-associated myoCAF genes was established and refined through deep learning methods. CD36 positive expression in CAFs can significantly promote the proliferation, migration, and invasion abilities of PTC cells, while inhibiting the apoptosis of PTC cells.

CONCLUSION

This study addresses the significant issue of LNM risk in PTC. Analysis of postoperative HE pathological slides from a substantial patient cohort reveals a notable association between high fibrosis density at the invasive front of the tumor and LNM. Integration of scRNA-seq data comprehensively analyzes CAF infiltration in PTC, identifying metastasis-associated myoCAFs with strong intercellular interactions. In vitro experimental results indicate that CD36 positive expression in CAFs plays a promoting role in the progression of PTC. Overall, these findings provide crucial insights into the function of CAF subset in PTC metastasis.

Predicting central cervical lymph node metastasis in papillary thyroid microcarcinoma using deep learning

Background

The aim of this study is to design a deep learning (DL) model to preoperatively predict the occurrence of central lymph node metastasis (CLNM) in patients with papillary thyroid microcarcinoma (PTMC).

Methods

This research collected preoperative ultrasound (US) images and clinical factors of 611 PTMC patients. The clinical factors were analyzed using multivariate regression. Then, a DL model based on US images and clinical factors was developed to preoperatively predict CLNM. The model's efficacy was evaluated using the receiver operating characteristic (ROC) curve, along with accuracy, sensitivity, specificity, and the F1 score.

Results

The multivariate analysis indicated an independent correlation factors including age ≥55 (OR = 0.309, p < 0.001), tumor diameter (OR = 2.551, p = 0.010), macrocalcifications (OR = 1.832, p = 0.002), and capsular invasion (OR = 1.977, p = 0.005). The suggested DL model utilized US images achieved an average area under the curve (AUC) of 0.65, slightly outperforming the model that employed traditional clinical factors (AUC = 0.64). Nevertheless, the model that incorporated both of them did not enhance prediction accuracy (AUC = 0.63).

Conclusions

The suggested approach offers a reference for the treatment and supervision of PTMC. Among three models used in this study, the deep model relied generally more on image modalities than the data modality of clinic records when making the predictions.

Choice of management strategy for papillary thyroid microcarcinoma: active surveillance or immediate surgery?

Overdiagnosis of papillary thyroid microcarcinoma (PTMC) is prevalent, and effective management of PTMC is an important matter. The high incidence and low mortality rate of papillary thyroid carcinoma (PTC) justify the preference for active surveillance (AS) over immediate surgery (IS), particularly in cases of low-risk PTMC. Japan began AS in the 1990s as an alternative surgical option for PTMC and it has shown promising results. The safety and efficacy of AS management in PTMC have been verified. However, AS may not be suitable for all PTMC cases. How to find the balance between the decision-making of AS and IS requires careful consideration. Therefore, we collected and analyzed the relevant evidence on the clinical strategies for PTC and discussed AS and IS from the perspectives of health, economic, and psychological aspects, to help clinicians in choosing a more appropriate clinical strategy for PTC.

Risk factors associated with high-risk nodal disease in patients considered for active surveillance of papillary thyroid microcarcinoma without extrathyroidal extension

Background

Active surveillance (AS) has become an alternative treatment approach for papillary thyroid microcarcinoma (PTMC). The purpose of this study is to uncover the clinicopathological factors associated with high-risk nodal disease in order to select proper candidates for AS of PTMC.

Methods

We retrospectively reviewed 5,329 patients with PTMC without extrathyroidal extension (ETE) who underwent thyroidectomy with central compartment neck dissection (CCND) between 2007 and 2021 at Seoul St. Mary's Hospital. Patients with more than five metastatic lymph nodes (MLNs) (higher-risk N1 disease) and/or lateral neck node metastases (N1b disease) were defined as having high-risk nodal disease. The clinicopathological factors associated with high-risk nodal disease were analyzed.

Results

A total of 415 (7.8%) patients had higher-risk N1 disease. These patients were younger on average, included a higher proportion of males, and had a larger tumor size and more frequent capsular invasion and multifocality compared with other patients. For the tumor size, a cutoff value of 0.65 cm was the best predictor of nodal risk groups. In a multivariate analysis, the independent risk factors associated with higher-risk N1 disease were younger age, male sex, tumor size >0.65 cm, and the presence of capsular invasion and/or multifocality. A total of 246 (4.6%) patients had N1b disease at initial diagnosis. In a multivariate analysis, the independent risk factors associated with N1b disease were younger age, male sex, tumor size >0.65 cm, and the presence of capsular invasion and/or multifocality.

Conclusions

Young age, male sex, tumor size >0.65 cm, and presence of capsular invasion and/or multifocality can be considered risk factors for high-risk nodal disease in PTMC. Therefore, cautious observation is necessary for AS of patients with these characteristics.

A novel nomogram for identifying high-risk patients among active surveillance candidates with papillary thyroid microcarcinoma

Objective

Active surveillance (AS) has been recommended as the first-line treatment strategy for low-risk (LR) papillary thyroid microcarcinoma (PTMC) according to the guidelines. However, preoperative imaging and fine-needle aspiration could not rule out a small group of patients with aggressive PTMC with large-volume lymph node micro-metastasis, extrathryoidal invasion to surrounding soft tissue, or high-grade malignancy from the AS candidates.

Methods

Among 2,809 PTMC patients, 2,473 patients were enrolled in this study according to the inclusion criteria. Backward stepwise multivariate logistic regression analysis was used to filter clinical characteristics and ultrasound features to identify independent predictors of high-risk (HR) patients. A nomogram was developed and validated according to selected risk factors for the identification of an HR subgroup among "LR" PTMC patients before operation.

Results

For identifying independent risk factors, multivariable logistic regression analysis was performed using the backward stepwise method and revealed that male sex [3.91 (2.58-5.92)], older age [0.94 (0.92-0.96)], largest tumor diameter [26.7 (10.57-69.22)], bilaterality [1.44 (1.01-2.3)], and multifocality [1.14 (1.01-2.26)] were independent predictors of the HR group. Based on these independent risk factors, a nomogram model was developed for predicting the probability of HR. The C index was 0.806 (95% CI, 0.765-0.847), which indicated satisfactory accuracy of the nomogram in predicting the probability of HR.

Conclusion

Taken together, we developed and validated a nomogram model to predict HR of PTMC, which could be useful for patient counseling and facilitating treatment-related decision-making.

Sentinel node mapping in thyroid cancer: an overview

In this paper we describe the current status of sentinel node mapping (SNM) in thyroid tumors and its potential perspectives. SNM in thyroid cancer has been tested since the end of the twentieth century, mainly in papillary thyroid cancer (PTC) and in medullary thyroid cancer (MTC). In PTC, it has been employed to find occult lymph node metastases in the central compartment of the neck as an alternative or indication for prophylactic dissection, by several methods. All of them have proven effective in spotting sentinel nodes, but the results have been somewhat diminished by uncertainty about the clinical significance of occult metastases in differentiated thyroid cancer. SNM in MTC has also been used to find occult lymph node metastases in the lateral compartments of the neck, also with excellent results hindered by a similar doubt about the real clinical significance of MTC micrometastases. Well designed, adequately sized randomized controlled trials are lacking, so SNM in thyroid tumors remains an interesting yet experimental methodology. New technology is emerging that could facilitate such studies, which could add solid information about the clinical significance of occult neck metastases in thyroid cancer.

Can Cervical Lymph Node Metastasis Increase the Risk of Distant Metastasis in Papillary Thyroid Carcinoma?

Background

Distant metastasis (DM) is a rare event and has a negative effect on the prognosis for papillary thyroid carcinoma (PTC). The relationship between cervical lymph node metastasis and DM is complicated and unclear. This study aimed to evaluate the impact of N stage subclassification on different distant metastasis sites based on age stratification, especially for patients with papillary thyroid microcarcinoma.

Methods

A total of 28,712 patient with PTC cases between 2010 and 2018 were extracted from the Surveillance, Epidemiology, and End Results database. Multivariable logistic regression analysis was utilized to adjust for confounding variables. Risk stratification, including positive lymph node number and lymph node ratio, was established by receiver operating characteristic curves to help predict DM.

Results

Lung was the most common metastatic site regardless of N0, N1a disease, or N1b disease. As the N stage increased, the higher the rate of DM identified. After age stratification, only N1b disease significantly increased the risk of lung metastasis (LM; odds ratio, OR = 20.45, P < 0.001) rather than bone metastasis (BM; OR = 3.46, P > 0.05) in younger patients. However, in older patients, N1b disease significantly increased the risk of both LM (OR = 4.10, P < 0.001) and BM (OR = 2.65, P = 0.007). In patients with papillary thyroid microcarcinoma (PTMC), N1a disease did not increase the risk of DM, LM, and BM compared with N0 disease (P > 0.05). Furthermore, combined N stage with risk stratification has well performance in predicting DM (area under the curve, AUC = 0.761). Similar results were shown in PTC patients with LM (AUC = 0.770) and BM (AUC = 0.729).

Conclusion

Overall, the incidence of DM significantly increased with the progress of N disease after age stratification. N1a disease did not increase the risk of DM in PTMC patients, regardless of LM or BM. Combined N stage with risk stratification may be beneficial for DM prediction.

Ultrasound-Guided Radiofrequency Ablation Versus Thyroid Lobectomy for Low-Risk Papillary Thyroid Microcarcinoma: A Propensity-Matched Cohort Study of 884 Patients

Background: Thermal ablation (TA) has been applied in patients with low-risk papillary thyroid microcarcinoma (PTMC) who refuse surgery or active surveillance (AS). Recently, TA has been proposed as a potential therapeutic option for patients who are suitable for surgery or AS. However, the clinical outcomes of TA versus surgery remains controversial because of a lack of sufficient data. This study aimed to compare the clinical outcomes between radiofrequency ablation (RFA) versus thyroid lobectomy (TL) for low-risk PTMC in a large cohort. Methods: This retrospective study evaluated 884 patients with unifocal low-risk PTMC treated with TL or RFA from June 2014 to March 2018. Among them, 460 patients underwent TL (TL group) and 424 patients, who refused surgery or AS, underwent RFA (RFA group). Patients were regularly followed up after treatment. Local tumor progression, recurrence-free survival (RFS), complications, and treatment variables, including procedure time, estimated blood loss, hospitalization, and cost, were compared after propensity score matching (PSM). Results: After PSM, a total of 332 patients underwent TL (mean ages 43.8 ± 9.5 years) and 332 underwent RFA (mean ages 44.1 ± 9.5 years). During the follow-up (median [interquartile ranges], 48.3 [23.2] months), no significant differences were observed in local tumor progression (1.8% vs. 3.3%, p = 0.209), lymph node metastasis (0.6% vs. 0.6%, p = 1.000), recurrent PTMC (1.2% vs. 2.4%, p = 0.244), persistent lesion (0% vs. 0.3%, p = 0.317), and 4-year RFS rates (98.2% vs. 97.0%, p = 0.223) between the TL and RFA groups. Distant metastasis was not detected. None of the patients who were treated by RFA underwent delayed surgery. Patients undergoing RFA had shorter procedure time (3.4 [2.5] vs. 86.0 [37.0] minutes, p < 0.001), lower estimated blood loss (0 vs. 20 [10.0] mL, p < 0.001), shorter hospitalization (0 vs. 7.0 [3.0] days, p < 0.001), lower cost ($2035.7 [254.0] vs. $2269.1 [943.4], p < 0.001) and lower complication rate (0% vs. 4.5%, p < 0.001) than those treated by TL. The association between treatment modality and recurrence remained nonsignificant after Cox analysis (p = 0.247). Conclusions: This large matched study revealed comparable four-year clinical outcomes between RFA and TL for low-risk PTMC. As a minimally invasive modality, RFA may be a promising alternative to the existing treatment options for low-risk PTMC.

Risk Factors of Central Lymph Node Metastasis in Papillary Thyroid Microcarcinoma and the Value of Sentinel Lymph Node Biopsy

Objective: The present study aims to investigate the risk factors of central lymph node metastasis (CNM) in papillary thyroid microcarcinoma (PTMC) and evaluate the predictive value of sentinel lymph node biopsy (SLNB) during surgery.

Methods: The clinicopathological data of 179 patients with PTMC staging in cN0 and with SLNB performed were analyzed retrospectively. Positive sentinel lymph node ratio (PSLNR) and additional positive lymph node (APLN) were analyzed in cases with positive SLNB. The efficiency of SLNB was investigated. ROC curves were plotted to evaluate the predictive value of PSLNR for APLN.

Results: Cumulative maximum diameter of tumors (CMD) (P = 0.041) and capsule involvement (CI) (P = 0.014) were independent risk factors for central lymph node metastasis. The SLNB success rate was 97.28%, and the incidence of CNM was 31.28%. The sensitivity, specificity, false positive rate (FPR), false negative rate (FNR), positive predictive value (PPV), and negative predictive value (NPV) of SLNB to evaluate CNM and APLN were 82.14 vs. 61.54%, 100 vs. 80.39%, 0 vs. 19.61%, 17.86 vs. 38.46%, 100 vs. 34.78%, and 92.48 vs. 92.48%, respectively. For cases with positive SLNB, subgroup analysis was performed according to APLN. The PSLNRs of true and false positive groups were 0.4620 ± 0.1744 and 0.2425 ± 0.1355, respectively (P < 0.001). Analyzing the predictive value of PSLNR by the ROC curve, the optimal diagnostic cutoff point was 0.2917 [AUC = 0.861 (95% CI: 0.757, 0.966), P < 0.001], and the sensitivity, specificity, FPR, FNR, PPV, and NPV of PSLNR were 87.50, 73.33, 26.67, 12.50, 63.64, and 91.67%, respectively.

Conclusion: CMD and CI are independent risk factors for central lymph node metastasis in PTMC. SLNB has good predictive value for CNM. For cases with positive SLNB, PSLNR could be used to predict the presence of APLN, which may provide a theoretical basis for intraoperative lymph node dissection.

YY1-induced up-regulation of FOXE1 is negatively regulated by miR-129-5p and contributes to the progression of papillary thyroid microcarcinoma

BACKGROUND

Papillary thyroid microcarcinoma (PTM) belongs to papillary carcinomas whose length is about 1.0 cm. According to previous studies, FOXE1 is a transcription factor involved in the progression of papillary thyroid carcinoma (PTC). However, its detailed upstream mechanism remains unknown in PTM.

OBJECTIVE

Our study aimed at detecting and verifying the up-regulation of FOXE1 in PTM cell lines.

METHODS

FXOE1 expression was detected in PTM and normal cells through RT-qPCR. Loss-of-function experiments were conducted to identify the effect of silenced FOXE1 on cell proliferation, apoptosis, migration and invasion. Mechanism experiments were carried out to explore the upstream molecular mechanism of FOXE1.

RESULTS

Knockdown of FOXE1 could lead to the inhibition on cell proliferation, migration and invasion while positively regulating cell apoptosis. Importantly, Yin-Yang-1 (YY1) could boost the transcription of FOXE1, thereby upregulating FOXE1. Also, the binding potential of miR-129-5p to FOXE1 was identified in PTM cells and MiR-129-5p could target FOXE1. In addition, the cellular processes in PTM were hindered with the increase of miR-129-5p expression level.

CONCLUSION

Our research suggested that the up-regulation of FOXE1 is regulated by YY1 and miR-129-5p, which may contribute to PTM progression.

Identification of Potential lncRNAs and miRNAs as Diagnostic Biomarkers for Papillary Thyroid Carcinoma Based on Machine Learning

BACKGROUND

Papillary thyroid carcinoma (PTC) accounts for most of the proportion of thyroid cancer (TC). The objective of this study was to identify diagnostic, differentially expressed long noncoding RNAs (lncRNAs) and microRNAs (miRNAs), contributing to understanding the epigenetics mechanism of PTC.

METHODS

The data of lncRNA, miRNA, and mRNA were downloaded from the Cancer Genome Atlas (TCGA) dataset, followed by functional analysis of differentially expressed mRNAs. Optimal diagnostic lncRNA and miRNA biomarkers were identified via random forest. The regulatory network between optimal diagnostic lncRNA and mRNAs and optimal diagnostic miRNA and mRNAs was identified, followed by the construction of ceRNA network of lncRNA-mRNA-miRNA. Expression validation and diagnostic analysis of lncRNAs, miRNAs, and mRNAs were performed. Overexpression of ADD3-AS1 was performed in PTC-UC3 cell lines, and cell proliferation and invasion assay were used for investigating the role of ADD3-AS1 in PTC.

RESULTS

A total of 107 differentially expressed lncRNAs, 81 differentially expressed miRNAs, and 515 differentially expressed mRNAs were identified. 11 lncRNAs and 6 miRNAs were regarded as the optimal diagnostic biomarkers for PTC. The epigenetic modifications via the above diagnostic lncRNAs and miRNAs were identified, including MIR181A2HG-FOXP2-hsa-miR-146b-3p, BLACAT1/ST7-AS1-RPS6KA5-hsa-miR-34a-5p, LBX2-AS1/MIR100HG-CDHR3-hsa-miR-34a-5p, ADD3-AS1-PTPRE-hsa-miR-9-5p, ADD3-AS1-TGFBR1-hsa-miR-214-3p, LINC00506-MMRN1-hsa-miR-4709-3p, and LOC339059-STK32A-hsa-miR-199b-5p. In the functional analysis, MMRN1 and TGFBR1 were involved in cell adhesion and endothelial cell migration, respectively. Overexpression of ADD3-AS1 inhibited cell growth and invasion in PTC cell lines.

CONCLUSION

The identified lncRNAs/miRNAs/mRNA were differentially expressed between normal and cancerous tissues. In addition, identified altered lncRNAs and miRNAs may be potential diagnostic biomarkers for PTC. Additionally, epigenetic modifications via the above lncRNAs and miRNAs may be involved in tumorigenesis of PTC.

Effects of Microwave Ablation on Papillary Thyroid Microcarcinoma: A Five-Year Follow-Up Report

Background: Some researchers have achieved favorable efficacy in the treatment of primary papillary thyroid microcarcinoma (PTMC) using microwave ablation (MWA). However, as PTMC is a slowly progressing disease, a long follow-up period is required to confirm treatment efficacy. Our study aim was to investigate the long-term efficacy and safety of ultrasound (US)-guided MWA in PTMC. Methods: In this study, 41 patients with thyroid masses (41 nodules) were diagnosed with PTMC by fine-needle aspiration or core needle biopsy. They underwent US-guided MWA. Preablation ultrasonic images of the thyroid nodules were collected, and the volumes were measured. The patients had follow-up at 1, 3, 6, and 12 months in the first year and every 6 months from the second year on, after MWA. The volume reduction rates (VRRs) of the thyroid nodules were analyzed. Results: In total, 40 of 41 nodules were completely ablated by MWA. After 60 months of follow-up, the volume significantly decreased from a median of 55.78 mm³ (quartile: 21.50, 112.20 mm³) to 0 mm³ (0, 0 mm³) (p < 0.001), with a VRR of 99.37% ± 4.02%. Two patients developed hoarseness after ablation; one recovered within 10 minutes, and the hoarseness in the other patient resolved 2 months after the ablation. No recurrence, metastatic cervical lymph nodes, or distal metastasis was found during the follow-up period. Conclusions: In this five-year follow-up, MWA presented favorable efficacy with satisfactory safety for the treatment of PTMC. It should be considered an alternative therapy to surgery and active surveillance for solitary PTMC.

Molecular Markers Guiding Thyroid Cancer Management

The incidence of thyroid cancer is rapidly increasing, mostly due to the overdiagnosis and overtreatment of differentiated thyroid cancer (TC). The increasing use of potent preclinical models, high throughput molecular technologies, and gene expression microarrays have provided a deeper understanding of molecular characteristics in cancer. Hence, molecular markers have become a potent tool also in TC management to distinguish benign from malignant lesions, predict aggressive biology, prognosis, recurrence, as well as for identification of novel therapeutic targets. In differentiated TC, molecular markers are mainly used as an adjunct to guide management of indeterminate nodules on fine needle aspiration biopsies. In contrast, in advanced thyroid cancer, molecular markers enable targeted treatments of affected signalling pathways. Identification of the driver mutation of targetable kinases in advanced TC can select treatment with mutation targeted tyrosine kinase inhibitors (TKI) to slow growth and reverse adverse effects of the mutations, when traditional treatments fail. This review will outline the molecular landscape and discuss the impact of molecular markers on diagnosis, surveillance and treatment of differentiated, poorly differentiated and anaplastic follicular TC.

Clinical and Ultrasonic Risk Factors for Lateral Lymph Node Metastasis in Papillary Thyroid Microcarcinoma: A Systematic Review and Meta-Analysis

Background: Clinical and ultrasonic risk factors for lateral lymph node metastasis (LLNM) in papillary thyroid microcarcinoma (PTMC) are not well-defined. Herein, a systematic review and meta-analysis was conducted to investigate clinicopathologic and ultrasonic risk features for LLNM in PTMC.

Methods: A systematic search of electronic databases (PubMed, Embase, Cochrane Library, and Web of Science) for studies published until April 2019 was performed. Case–control studies and randomized controlled trials that studied clinical and ultrasonic risk factors of LLNM in PTMC were included.

Results: Fourteen studies (all retrospective studies) involving 43,750 patients met final inclusion criteria. From the pooled analyses, younger age<45 (OR, 1.55; 95% CI, 1.16–2.07; P = 0.003), male patients (OR, 1.94; 95% CI, 1.55–2.42; P < 0.00), extrathyroidal extension (OR, 3.63; 95% CI, 2.28–5.77; P <0.00), tumor multifocality (OR, 2.24; 95% CI, 1.53–3.28; P <0.00), tumor > 0.5 cm (OR, 2.24; 95% CI, 1.53–3.28; P < 0.00), central lymph node metastasis (OR, 5.61; 95% CI, 4.64–6.79; P < 0.00), >25% tumor contact with thyroid capsule (OR, 6.66; 95% CI, 1.96–22.65; P = 0.002), tumor calcification (OR, 2.90; 95% CI, 1.71–4.93; P < 0.00), upper tumor (OR, 3.18; 95% CI, 2.23–4.55; P < 0.00) were significantly associated with increased risk of LLNM in PTMC, while Hashimoto's thyroiditis and other ultrasonic features (solid tumor, hypoechoic tumor, smooth margin, and taller than wide tumor) were not significantly associated with LLNM in PTMC.

Conclusions: Our analysis identified several clinicopathologic and ultrasonic factors associated with LLNM in PTMC. This finding highlights the need for a cautious and frequent postoperative surveillance of the lateral neck in high-risk PTMC patients. Moreover, high-risk ultrasonic features also need to be considered during selection of PTMC for active surveillance.

Low-risk papillary thyroid microcarcinoma: Optimal management toward a more conservative approach

The incidence of papillary thyroid microcarcinoma (microPTC) has dramatically increased in the last decades. Most of these tumors remain small and clinically "silent", only small number progress. Although thyroid surgery used to be the only therapeutic approach, recent guidelines now consider active surveillance for low-risk microPTC. For this reason, more accurate risk stratification of microPTC is needed. The optimal management of low-risk microPTC through accurate risk stratification represents a major clinical issue.

Predictive Factors of Lymph Node Metastasis in Patients With Papillary Microcarcinoma of the Thyroid: Retrospective Analysis on 293 Cases

Introduction: Papillary thyroid microcarcinoma (PTMC) is defined as a tumor with a larger diameter ≤ 1 cm and is considered having an indolent course and an excellent prognosis. Nevertheless, the incidence of lymph node metastasis in PTMC is not negligible, reaching up to 65% in some series. The aim of this study was to assess the incidence of lymph node metastasis in patients with PTMC and to evaluate predictive factors for lymph node metastasis. Methods: We included in this retrospective observational study patients who underwent thyroidectomy with pathological diagnosis of PTMC at our department from January 2003 to June 2019. Results: Two hundred ninety-three patients were included in the study. The incidence of lymph node metastasis was 13.7%. Multivariate analysis revealed as independent risk factors for lymph node metastasis age <45 years, nodule size ≥6 mm, tall cell variant of PTC, extrathyroidal extension, and angioinvasion. Conversely, autoimmune thyroiditis was found as a protective factor for lymph node metastasis. A subgroup of patients, with nodule size ≤ 5 mm, presented non-aggressive features. Conclusion: The incidence of lymph node metastasis in PTMC is considerable; the size of the tumor appears to be the most significant predictive factor for lymph node metastasis. The traditional cut-off value used for definition of microcarcinoma could be reconsidered to identify patients with an indolent course of the tumor, where active surveillance could be the appropriate treatment, and on the other hand, patients with potentially aggressive tumors requiring an adequate surgical intervention. Clinical Trial Registration: The trial was registered at ClinicalTrials.gov (ID: NCT04274829).

Lenvatinib for thyroid cancer treatment: discovery, pre-clinical development and clinical application

Introduction: About one third of patients affected with thyroid cancer present with recurrent disease. Unresectability, advanced disease and radioiodine refractoriness are considered poor prognostic factors. Treatment with small molecules inhibiting molecular signaling can be considered for patients with progressive disease, when other therapeutic strategies cannot be applied. Lenvatinib is a tyrosine kinase inhibitor targeting multiple molecular factors involved in angiogenesis and tumor progression. Preclinical studies have demonstrated the utility of lenvatinib as a targeted therapy for different tumors, including both differentiated and anaplastic thyroid cancer.Areas covered: The authors provide an overview of the preclinical development of lenvatinib in the treatment of thyroid cancer and review its clinical application. They also provide their expert opinion on its development.Expert opinion: Preclinical studies have helped in the understanding of the mechanisms of thyroid carcinogenesis and in the development of a targeted therapy. These findings have represented the rationale for the use of lenvatinib in clinical trials, which have confirmed its utility but yet failed to prove a clear benefit in overall survival. The decision to start a systemic treatment with lenvatinib must be personalized for each patient evaluating the risk/benefits ratio. Treatment emergent adverse events must be considered and reasonably managed by a multidisciplinary approach.

Which papillary thyroid microcarcinoma should be treated as "true cancer" and which as "precancer"?

BACKGROUND

Papillary thyroid microcarcinoma (PTMC) generally is a cancer with excellent prognosis, but the term "cancer" sounds severe and harsh, which can elicit emotional and physical responses from patients. To eliminate the word "cancer," the term noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was introduced. However, not all PTMCs can be classified as NIFTP. Sometimes, very aggressive PTMC cases might be observed. Some authors suggest that one of the risk factors for poor prognosis is lymph node metastasis. The aim of the study was to evaluate some clinicopathological features of PTMC as the risk factors for lymph node metastasis.

MATERIAL AND METHODS

We performed a retrospective chart review and selected 177 patients with PTMC. To analyze the cases with potentially aggressive behavior, we enrolled PTMC patients with lymph node metastases (pN1, central, and/or lateral) and evaluated some of their clinicopathological features.

RESULTS

The logistic regression analysis results demonstrated significantly higher rates of multifocal or bilateral tumor occurrence in the PTMC patients with pN1 than in the patients with pN0 (P < 0.0001 for both). In addition, the occurrence of thyroid tumors with sizes above 0.5 cm was a significant risk factor for lymph node metastasis (P < 0.0001). The results of the ROC analyses showed that the presence of multifocal or bilateral tumors and tumor sizes above 0.5 cm were significant predictors of lymph node metastasis (P < 0.0001 for all).

CONCLUSIONS

Multifocal and bilateral PTMC tumors with diameters above 0.5 cm should be treated aggressively as "true cancer" and might benefit from lymph node dissection. Unifocal PTMC tumors with diameters equal to or below 0.5 cm may be treated less aggressively.