Papillary thyroid microcarcinomas: does subtyping predict aggressive clinical behavior?

Papillary microcarcinoma of the thyroid gland: Evaluation of TERT and BRAFV-600E expression and their relationship with clinicopathological findings

Papillary microcarcinomas (PMCs) are papillary carcinomas ≤1 cm in size, with an increasing incidence. Although generally indolent, some cases exhibit aggressive behavior. Recently, active surveillance has been recommended to avoid surgical treatment. Identifying molecular changes that predict aggressiveness in PMCs has gained importance, but studies are limited. We aimed to demonstrate TERT expression and BRAF V600E positivity immunohistochemically in PMCs and correlate them with histomorphological features, subtypes, and clinicopathological findings. We included 95 PMC cases diagnosed between 2010 and 2019 at the Department of Pathology, Faculty of Medicine, XXX University. We investigated TERT expression using RT-PCR. We evaluated BRAF V600E mutation immunohistochemically. We evaluated the relationship between genetic, histomorphological, and clinicopathological findings. In patients with multifocality and those with a tumor size ≥0.5 cm, the frequency of lymph node metastasis was significantly higher. A positive correlation was shown between BRAF V600E positivity and lymph node metastasis, lymphovascular invasion, advanced disease stage, and classical subtype by univariate analyses. We detected TERT expression in 18 of 95 patients (7.8 %). No relationship could be detected between TERT expression alone or combined with BRAF positivity and clinicopathological features. Although TERT mutations are associated with aggressiveness in thyroid cancers, this association was absent in PMCs. The presence of TERT expression was demonstrated in some cases. However, TERT expression could not be associated with clinicopathological findings, which is consistent with the literature suggesting that TERT plays a role in advanced stages of carcinogenesis.

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.

Does the Presence of Capsule Influence Prognosis in Poorly-Differentiated Thyroid Carcinoma?

We collected all cases of poorly-differentiated thyroid carcinoma at our institution diagnosed between 2007-2022 to investigate the role of tumor capsule in these neoplasms along with other histologic factors that may lead to adverse patient outcome. After the exclusion of those meeting criteria for differentiated high-grade thyroid carcinoma or anaplastic carcinoma, we were left with 65 cases with a poorly-differentiated component. Four of those cases (6.2%) were entirely encapsulated with no invasion of the tumor capsule. Unencapsulated tumors showed significantly greater rates of extrathyroidal extension (75.0% vs. 41.5%) and death from disease (45.5% vs. 12.5%) than encapsulated tumors, regardless of capsular invasion, with no differences in sex, tumor size, angioinvasion, local recurrence, or metastasis. Compared with encapsulated tumors with invasion, encapsulated tumors without capsular invasion showed a strong male predominance (100% vs. 38.8%). No encapsulated tumors without capsular invasion demonstrated local recurrence, metastasis, or death from disease. No differences in percentage of poorly-differentiated components were noted among the three groups although there was a trend for encapsulated tumors to have a higher amount of poorly-differentiated component than unencapsulated tumors. We conclude that invasive tumors lacking a capsule demonstrate greater rates of disease-related death despite showing similar adverse histologic features to invasive encapsulated tumors. Moreover, we confirm that encapsulated tumors without capsular invasion have excellent long-term outcomes in terms of recurrences, metastases, and survival.

Efficacy and safety of ultrasound-guided radiofrequency ablation for papillary thyroid microcarcinoma: a systematic review and meta-analysis

BACKGROUND

We comprehensively evaluate the efficacy and safety of US-guided radiofrequency ablation (RFA) in the treatment of papillary thyroid microcarcinoma (PTMC) via a systematic review and meta-analysis.

METHODS

We searched the PubMed, Embase and Cochrane Library databases for studies published during the time between the establishment of the database through October 2021. We included a 10 non-randomized controlled trial (non-RCT) that reported the application of US-guided RFA in PTMC. The sample size of patients totaled 1279. We evaluated the ablation efficacy by analyzing the volume reduction rate (VRR), complete disappearance rate (CDR) and recurrence rate of PTMC treated by RFA. We analyzed all data using STATA version 15.1 (Stata Corporation, College Station, TX).

RESULTS

Our pooled results proved RFA treatment significantly reduces the volume of tumors (Weighted Mean Difference [WMD] = -103.20, 95% CI: -111.93 - -94.48, p = 0.000). We also found the VRR at 12 months after RFA was 93.27% (95% CI: 84.68-101.86), and the CDR at 12 months after RFA was 64% (95% CI: 39-89%). Additionally, pooled results showed the incidence of mPTC residue in ablation area, newly discovered mPTC and lymph node metastases after RFA treatment were respectively 0.3% (95% CI: -0.1-0.7%), 2.5% (95% CI: 1.1-3.9%) and 1.0% (95% CI: 0.2-1.9%), and the incidence of complications after RFA treatment was 1.8% (95% CI: 0.7-3.2%).

CONCLUSIONS

US-guided RFA is effective and safe for treating PTMC. It could be an excellent alternative to the existing treatment options.

Reconceptualize tall-cell variant papillary thyroid microcarcinoma: From a "sonographic histology" perspective

OBJECTIVE

This study aimed to examine the relationship between sonographic features and histological manifestations in the tall-cell variant of papillary thyroid microcarcinoma (TCV-PTMC), thus proposing the concept of "sonographic histology" and examine its value in the clinical management of the aggressive tall-cell variant.

METHODS

This study retrospectively included 104 participants who were admitted to Peking University Third Hospital from 2015 to 2022 and were histopathologically confirmed as having TCV-PTMC or classical PTMC. We mainly compared the general characteristics, sonographic characteristics, and pathological specimens between the two cohorts.

RESULTS

Hypoechoic nodules with a localized central isoechoic lesion and hypoechoic halo around nodules were most often observed in TCV-PTMC, which correlated with circumferentially distributed tumor epithelium and densely distributed tumor stroma histopathologically. Additionally, TCV-PTMC showed nodules with a more regular margin and less microcalcification than classical PTMC, which led to an underestimation of the risk of TCV-PTMC.

CONCLUSION

The good association between the ultrasound echo pattern and tissue cell arrangement was defined as sonographic histology in this study and can be applied in the preoperative identification of TCV-PTMC. This concept may provide novel insight for the identification of special subtypes of thyroid tumors and may modify pitfalls of the Thyroid Imaging Reporting and Data System in aggressive variants of microcarcinoma.