RASGEF1C methylation for the distinguishment and classification of benign and malignant thyroid tumors.

Background: The incidence of thyroid cancer (TC) has significantly increased, highlighting the need for effective and objective approaches for the early diagnosis of TC. This study aimed to explore RASGEF1C methylation as a biomarker for papillary thyroid cancer (PTC).

Methods: Formalin-fixed paraffin-embedded samples from a total of 363 PTC and 409 benign thyroid nodules from multiple centers were analyzed. RASGEF1C methylation profiles were examined via MALDI-TOFF mass spectrometry. Statistical analysis was performed via logistic regression adjusted for covariates, nonparametric tests, and receiver operating characteristic (ROC) analysis. Additionally, 40 follicular thyroid cancer samples, 45 medullary thyroid cancer samples, and 7 anaplastic thyroid samples from three hospitals were afterward collected to compare methylation patterns across subtypes.

Results: Hypomethylation of RASGEF1C in PTC was observed vs. BTN (all odds ratios (ORs) ≥ 1.57, p values < 0.001). Stratification analysis revealed a more pronounced association in younger patients, especially for BRAF V600E-positive PTC patients, than in individuals with benign tumors (all ORs ≥ 1.89, p values < 0.001). ROC analysis further demonstrated the outstanding diagnostic power of RASGEF1C hypomethylation for BRAF V600E-positive PTC cases (area under the curve (AUC) = 0.93), for cases < 55 years old (AUC = 0.88), and even for patients with a tumor length ≤ 1 cm (AUC = 0.83). Moreover, we observed the lowest RASGEF1C methylation level in anaplastic thyroid carcinoma, the most aggressive subtype of TC. Our results revealed similar RASGEF1C hypomethylation between chronic lymphocytic thyroiditis and papillary thyroid cancer, whereas RASGEF1C methylation in subacute thyroiditis patients was similar to that in the other benign subtypes.

Conclusion: Our study revealed RASGEF1C methylation as a promising biomarker for distinguishing and classifying benign and malignant thyroid tumors and even provided epigenetic evidence for the inflammatory-cancer transformation. Nevertheless, the limitation of tissue-based biomarkers should be well noted, and the development of more accessible biomarkers warrants further exploration in the future.