Metastatic prostatic carcinoma to testis: histological features mimicking lymphoma

We report a case of prostatic carcinoma with testicular metastasis, which mimicked malignant lymphoma of the testis. The patient was a 71 year-old man with a history of prostate adenocarcinoma of Gleason score 9 (4+5) diagnosed in 2001 for which he received hormonal therapy. Four years later, the patient developed multiple osteoblastic bone metastases. Radiotherapy of the bone metastases was given with subsequently bilateral orchiectomy for hormonal deprivation therapy in May 2005. Grossly, one of the testes had a subcapsular rubbery 0.9 cm nodule. Microscopically, the nodule was composed of malignant discohesive cells predominantly infiltrating in the interstitium with an appearance of malignant lymphoma. However, immunohistochemical stains were positive for prostate-specific antigen and prostate acid phosphatase and negative for leukocyte common antigen, which confirmed the diagnosis of metastatic prostate adenocarcinoma.