Prostate specific antigen (PSA), placental alkaline phosphatase (PAP), S100, vimentin, alpha fetoprotein (AFP), calretinin, and leukocyte common antigen staining can be performed to exclude other types of tumors including metastatic prostate cancer, melanoma, sarcoma, testicular tumor, mesothelioma, and lymphoma. The gene discussed is KLK3; the disease is lymphoma.