Furthermore, more direct evidence from a study [32] comparing genomic alterations in the transition from cervical intraepithelial neoplasia (CIN) to microinvasive carcinoma (MIC) and cervical squamous cell carcinoma (CESC) revealed that PIK3CA was altered in the MIC and CESC either by mutation or amplification but not in the CIN, indicating that mutations such as PIK3CA, TP53, STK11 and MAPK1 are needed in the transition from CIN to MIC or CESC, in addition to human papilloma virus infection. Here, STK11 is linked to cervical squamous cell carcinoma.