Octamer-binding transcription factor 4 (Oct-4), also known as POU5F1 (POU domain, class 5, transcription factor 1), is a member of the POU homeodomain family of transcription factors and is involved in the maintenance and regulation of pluripotency in embryonic stem and germ cells. Anti-Oct-4 is highly useful and sensitive for seminomas, germinoma, dysgerminoma, embryonal carcinoma, and gonadoblastoma. Oct-4 may be associated with tumorigenesis, and can have an effect on some aspects of tumor behavior, including tumor recurrence or resistance to therapies.