Metastatic Tumors in Testis : Diagnosis
The diagnosis of metastasis can usually be made (or at least narrowed down to a small number of entities) on H&E stains. Confirmation of the site of origin and distinction between metastases and primary testicular tumors may require ancillary studies. Lineage-specific immunohistochemical stains can be helpful (e.g. TTF-1 and PSA). The image shows strong immunoreactivity for PSA in metastatic prostate cancer in the testis. The tumor forms diffuse sheets without any discernible acini (see H&E in the previous image). Patient had a history of prostatic adenocarcinoma (Gleason score 4+5=9; Grade group 5). If embryonal carcinoma or seminoma are in the differential, OCT3/4 is useful because of its sensitivity and specificity for these two tumors. EMA is positive in most metastatic carcinomas but negative in germ cell tumors.