POU5F1 and cervical squamous intraepithelial neoplasia: Ten studies [20–29] included 408 CC cases, nine studies [20–26,28,29] reported the expression of OCT-4 in CC and normal cervical tissues, four studies [23,24,26,27] reported OCT-4 expression in the CC tissue and CIN tissue groups, three studies [23,24,26] reported OCT-4 expression in the CIN tissue and normal cervical tissues, three studies [24,26,27] reported OCT-4 expression in the CIN I + II tissue and CIN III tissues, six studies [21,22,24,26,28,29] reported the expression of OCT-4 in CC with different degrees of differentiation.