RASSF1 and thyroid cancer, nonmedullary, 2: Hypermethylation of RASSF1, a known tumor suppressor gene, has been described in 75% of FTC, a smaller percentage of benign adenomas (44%), and PTC (20%) (Xing, Cohen, Mambo, Tallini, & Udelsman, 2004) indicating that this may be an early step in follicular cell derived thyroid tumorigenesis.