NKX3.1 and Prostein Expression in Testicular Tissue and Sex Cord-stromal Tumors

Prostate cancer is well known to metastasize to the testis and is not an uncommon finding on castration performed for advanced disease. Although germ cell tumors make up the majority of testis neoplasms, there are more rare tumors, such as rete testis adenocarcinoma, that can mimic metastatic disease. NKX3.1 and prostein (P501S) are antibodies highly specific for prostate origin. Relatively little is known of the expression of these markers in testicular tissue. We investigated the expression of NKX3.1 and P501S in testicular tissues, sex cord-stromal tumors, germ cell tumors, and rete testis adenocarcinoma. We found strong diffuse nuclear staining for NKX3.1 in Sertoli cells of the testis. Expression of NKX3.1 was seen in 0/3 ovarian Sertoli cell tumors, 1/4 testicular Sertoli cell tumors, and in the Sertoli cell component of 1/12 ovarian Sertoli-Leydig cell tumors. We found moderate, diffuse cytoplasmic positivity for P501S in rete testis epithelium and in testicular Leydig cells. P501S also highlighted Leydig cells in 9/12 Sertoli-Leydig cell tumors of the ovary. Two of 3 Leydig cell tumors of the testis showed weak to moderate, diffuse cytoplasmic staining for P501S. All cases of embryonal carcinoma and pure seminoma were negative for both NKX3.1 and P501S. One case of rete testis adenocarcinoma showed patchy positivity for both NKX3.1 and P501S. In conclusion, NKX3.1 shows routine expression in Sertoli cells and P501S shows routine expression in Leydig cells and rete testis epithelium. In addition, these markers can be positive in sex cord-stromal tumors and rete testis adenocarcinoma.