POU5F1 and in situ carcinoma: The overall findings resulted in the conclusion that OCT3/4 is an excellent, and currently successfully used, diagnostic marker for the detection of undifferentiated variants of so-called type II GCTs (UNDIF-GCTs=SE or dysgerminoma/germinoma, and the stem cell component of non-seminoma (NS, specifically embryonal carcinoma)), as well as their precursor stages (carcinoma in situ of the testis (CIS) and gonadoblastoma of dysgenetic gonads) (Looijenga et al, 2003; de Jong et al, 2005, 2008b; de Jong and Looijenga, 2006; Cheng et al, 2007).