OCT4: A sensitive and specific biomarker for intratubular germ cell neoplasia of the testis.

PURPOSE OCT4 (POU5F1, OCT3) immunostaining highlights pluripotent cells (embryonal carcinoma and seminoma) in primary testicular germ cell tumors, but its relative usefulness in diagnosing intratubular germ cell neoplasia, unclassified (IGCNU) is not well established. The present study aimed to establish OCT4 as a sensitive and specific maker for IGCNU, a putative precursor for adult germ cell tumors. EXPERIMENTAL DESIGN We evaluated OCT4 immunostaining in 44 cases of IGCNU from patients who had testicular germ cell tumors. In addition, 27 of the 44 IGCNU sections were also examined with antibodies to placenta-like alkaline phosphatase, the most frequently used immunohistochemical marker for intratubular germ cell neoplasia. Sections from the testes of 10 patients who had undergone orchiectomy for hormonal treatment of prostate cancer and from autopsies of 10 patients without histories of germ cell tumors were also examined for OCT4 immunostaining. The immunoreactivity of the autopsy tissues was determined with vimentin staining, and all were reactive. RESULTS In all 44 of the cases, antibody to OCT4 marked the nuclei of nearly all of the dysplastic cells of intratubular germ cell neoplasia but not non-neoplastic testicular cells. The staining intensity was strong in every case, and there was little or no background staining. All 20 of the control specimens (10 orchiectomy specimens from prostate cancer patients and 10 testes from autopsies) were completely negative for OCT4. The 27 cases that were stained with antiplacenta-like alkaline phosphatase antibodies showed staining of variable intensity in the areas of intratubular germ cell neoplasia, and there was a high level of background staining artifact. CONCLUSIONS OCT4 is a sensitive and specific maker for intratubular germ cell neoplasia.