There were 67 primary chordoma cases, and mutations were observed in ARID1A (n = 5; 7.5%), PIK3CA (n = 5; 7.5%), TP53 (n = 4; 6.0%), and PBRM1 (n = 4; 6.0%), as seen in Table 5. The gene discussed is PIK3CA; the disease is chordoma.