Consensus Statement: Recommendations on Actionable Biomarker Testing for Thyroid Cancer Management

Comprehensive Gene Expression Analysis in Papillary Thyroid Carcinoma Reveals a Transcriptional Profile Associated with Reduced Radioiodine Avidity

Papillary thyroid carcinoma (PTC) is the most common form of well-differentiated thyroid cancer (WDTC) and generally has a favorable prognosis. However, subsets of these tumors can metastasize, leading to aggressive disease progression and poorer clinical outcomes. Radioactive iodine (RAI) therapy is routinely given in the adjuvant setting following thyroidectomy and lymph node dissection for WDTC. Nevertheless, its therapeutic efficacy is limited to tumors with high iodine avidity. Early post-surgical classification of thyroid cancers as either iodine-avid or refractory is crucial for enabling more personalized and effective treatment strategies. In this study, we aimed to identify transcriptomic determinants associated with RAI refractoriness (RAI-R) to improve prognostication. We collected clinicopathologic data and conducted RNA-seq on 36 tissue samples (18 high-avidity and 18 low-avidity), each uniquely characterized by ex vivo iodine concentration measurements taken directly from surgical specimens. Whole-transcriptomic analysis identified 63 differentially expressed genes, with six (S100A4, CRTC2, ANO1, WWTR1, DEPTOR, MT1G) showing consistent deregulation. The expression of ANO1, an established iodine transporter at the apical membrane of the thyroid follicular cells, correlated significantly with iodine avidity (r = 0.54). Validation via RT-qPCR confirmed differential expression trends. Gene ontology and pathway enrichment analyses highlighted thyroid hormone synthesis, PI3K-AKT, and MAPK signaling pathways as key regulators of RAI avidity. A refined multivariate predictive model incorporating ANO1 mRNA expression, histological subtypes, and sample type demonstrated strong predictive performance (adjusted R2 = 0.55). These findings suggest ANO1 as a promising biomarker for predicting iodine avidity in thyroid cancer.

Identification of Oncogenic Alterations in 124 Cases of Pediatric Papillary Thyroid Carcinoma: BEND7::ALK, DLG5::RET, and CCDC30::ROS1 Fusions Induce MAPK Pathway Activation

Pediatric papillary thyroid carcinoma (PPTC; under age 18 at the time of diagnosis) is relatively uncommon. There are few studies concerning the genetic background of PPTC in Asian countries. In this study, we reviewed 124 cases of PPTC from a single medical center in China. DNA-based next-generation sequencing (NGS) was performed to identify genetic alterations, with receptor tyrosine kinase (RTK) fusions further validated by RNA-based NGS. DICER1 mutations and TERT promoter mutations were detected by Sanger sequencing. We also explored the relationship between these genetic alterations and the clinicopathologic features, as well as the prognostic factors. Three recombinant plasmids expressing V5/HIS-tagged RTK fusion proteins (BEND7::ALK, DLG5::RET, CCDC30::ROS1) were constructed to investigate the in vitro effects. We found that the two most common subtypes were the classic subtype (77.4%) and the diffuse sclerosing subtype (17.7%). Hashimoto's thyroiditis was observed in 42.3% of cases, and regional lymph node metastasis was present in 82.9% of patients. The most frequent genetic alteration was the BRAF c.1799 T > A (p.V600E) mutation (63 patients, 50.8%), followed by RTK fusions (31 patients, 25.0%). A DICER1 mutation was detected in two cases, and TERT promoter mutations were not observed in any of the patients. RTK fusions were associated with the diffuse sclerosing subtype, Hashimoto's thyroiditis, and extrathyroidal extension. Adverse prognostic factors identified included RTK fusion, age under 14 years, and tumor size over 2 cm. Additionally, a significant proportion of these patients had actionable molecular alterations. Three rare kinase fusions, BEND7::ALK, DLG5::RET, and CCDC30::ROS1, were shown to induce phosphorylation of the MAPK pathway and promote cell proliferation in vitro. The specific RTK inhibitors could counteract the fusion-induced cell proliferation. Our data highlights the genetic landscape of Chinese PPTC patients, with RTK fusions being associated with aggressive clinicopathologic features. The rare fusions BEND7::ALK, DLG5::RET, and CCDC30::ROS1 may contribute to PPTC development with a BRAF-like effect.