A study of copy number alterations also showed a consistent degree of intratumor heterogeneity, with some CNA events being subclonal and emerging in the late stages of tumor development; genes involved in cell cycle regulation, such as TP53, CCND1, RB1, CDK6 and CDKN2A, displayed early-occurring CNAs, while alterations of RTK/RAS/PI3K genes were usually late-occurring events [43]. Here, PIK3CA is linked to neoplasm.