CCND2 and in situ carcinoma: This hypothesis is based on the strict similitude between primordial germ cells and gonocytes with tumor cells of the carcinoma in situ (CIS), verified at the molecular level by the shared expression of genes involved in pluripotency and proliferation, such as NANOG, STELLAR, DPPA-5, GDF3, K-RAS, and CCND2 (126–129).