(Octamer transcription factor-3/4)
OCT3/4 (OCT4, FOU5F1) is a nuclear POU-domain octamer binding transcription factor specifically expressed in cells with pluripotent capacity, i.e., embryonic stem cells and germinal cells. The gene is located on chromosome 6p21.3.
In virtually all cases of seminoma/dysgerminoma/germinoma, embryonal carcinoma, and the germ
cell component of gonadoblastoma, OCT3/4 is expressed strongly in more than 90% of
the nuclei, sometimes with a dot-like cytoplasmic reaction as well. Also the germinal tumour precursor lesion, intratubular germ cell neoplasia unclassified (IGCNU), is strongly stained. OCT3/4 is not found in other germ cell tumours (spermatocytic seminoma, choriocarcinoma or yolk sac tumour). Other tumour types are virtually always negative (very rarely, staining – mostly focal and weak – has been seen in carcinomas of the bladder, kidney and lung, and in Ewing sarcoma).
Classification of germ cell tumours, viz. identification of seminoma/dysgerminoma/germinoma, embryonal carcinoma, and gonadoblastoma, as well as IGCNU. OCT3/4 gives a better signal/noise ratio than placental alkaline phosphatase (PLAP) in seminoma and related tumours, and is more sensitive than CD30 in embryonal carcinoma, particularly after chemotherapy (where CD30 is frequently lost).
IGCN is recommended as a positive control in which the staining must be as strong as possible in the nuclei of the neoplastic cells, whereas no nuclear staining should be seen in other cells.
29.06.12 - MV/LE