RRAS2, also known as teratocarcinoma oncogene 21 (TC21), being originally cloned from a human teratocarcinoma cDNA library (A. M. Chan, Miki, Meyers, & Aaronson, 1994), shares >50% amino acid sequence homology with HRAS, which reaches 80% when excluding the hypervariable C‐terminal tail. The gene discussed is RRAS2; the disease is teratocarcinoma.