Background: Epigenetic alterations such as DNA methylation are widespread cancer, contributing to tumorigenesis and acting as markers for prognostication. Papillary thyroid cancer (PTC) demonstrates tumor-specific methylation of numerous genes, including RASSF1A. Although the function of RASSF1A in PTC tumorigenesis is still being defined, quantitative evaluation of RASSF1A methylation and its correlation with tumor characteristics has not been performed.
Methods: Analysis of RASSF1A methylation was performed using quantitative polymerase chain reaction after methylation-dependent and -sensitive restriction enzyme digestion in PTC (n = 41) and normal (n = 18) thyroid tissue. Methylation was then evaluated for correlation with tumor size, stage, and multiple histopathologic characteristics.
Results: RASSF1A promoter hypermethylation was observed in nearly all PTC cases versus normal thyroid tissue, with mean hypermethylation 4.2 times greater in PTC (P < .05). Hypermethylation was greater in multifocal than unifocal PTC (P < .05). Furthermore, tumor methylation was inversely correlated with extracapsular invasion (P < .05).
Conclusion: RASSF1A methylation differs in PTC compared with normal thyroid, is associated with multifocality, and is inversely correlated with extracapsular invasion. The ease of evaluating methylation status with minute amounts of DNA suggests a potential role for RASSF1A as a molecular marker for characterization of PTC histopathology.