A Rare Case of Scrotal Swelling: Prostate Cancer Metastasis Masquerading as a Complicated Hydrocele.

Metastasis of prostate cancer to the testes is exceptionally rare. We report the case of a 67-year-old male with a 10-year history of high-risk prostate cancer, previously treated and currently in remission, who presented with left scrotal swelling. The swelling was clinically and radiologically diagnosed as a hydrocele and treated surgically. A postoperative localized infection complicated the hydrocele repair. Two years after the surgery, the patient presented with a reoccurrence of scrotal swelling, coinciding with an insignificant increase in serum prostate-specific antigen (PSA) levels from 0.4 ng/mL to 2.0 ng/mL. Furthermore, computed tomography (CT) imaging of the abdomen and pelvis demonstrated no suspicious masses and normal appearance of the underlying testes. However, repeat ultrasonography of the left testis revealed an irregular and diffusely heterogeneous testis with increased vascularity. Presuming these findings to be fibrotic scrotum following a hydrocele repair complicated with postoperative infection, a left inguinal orchidectomy was performed. Histopathological analysis revealed extensive infiltration of the testicular parenchyma by adenocarcinoma, characterized by cribriform glands, round nuclei, and prominent nucleoli. Immunohistochemical analysis revealed widespread positivity for PSA and moderate, patchy expression of NKX3.1. Additionally, there was focal, strong staining for chromogranin and synaptophysin. A collaborative evaluation by the multidisciplinary team involving urological surgeons, pathologists, and radiologists was crucial in reaching the final diagnosis of metastatic prostate adenocarcinoma to the testis. This case emphasizes the importance of maintaining a high suspicion for metastasis in prostate cancer patients, even when clinical or radiological findings are not prominent, as the diagnostic approach may not always follow a predictable course.