POU5F1 and embryonal carcinoma: Due to the growing interest in tumor stemness, a lot of results have been accumulated concerning the expression of OCT4 variants in tumors of different localization, and although OCT4A expression is limited to embryonic cells and embryonic carcinoma cells, it has been noted that OCT4B is expressed in human somatic stem cells, tumor cells, adult tissues, and pluripotent cells [78,79,80,81,82].