Testicular germ cell tumor (TGCT) is the most common solid malignancy occurring in young men between 20 and 34 years of age, and its incidence has increased significantly over the last decades. Clinically several types of immunohistochemical markers are useful and sensitive. These new biomarkers are genes expressed in primordial germ cells/gonocytes and embryonic pluripotency-related cells but not in normal adult germ cells and they include OCT3/4, HMGA1 and 2, NANOG, SOX2, and LIN28. Gene expression in TGCT is regulated, at least in part, by DNA and histone modifications, and the epigenetic profile of these tumours is characterised by genome-wide demethylation. There are different epigenetic modifications in TGCT subtypes that reflect the normal developmental switch in primordial germ cells from an under to normally methylated genome.