Solitary Testicular Metastasis From Ductal Prostate Cancer 5 Years After Radical Prostatectomy: A Case Report

Testicular metastases from prostate carcinoma are exceedingly uncommon, particularly from the ductal histological subtype, which is associated with aggressive clinical behavior and a propensity for atypical metastatic dissemination. We report the case of a 73-year-old male with a history of prostate ductal adenocarcinoma (PDA) treated in 2018 with robot-assisted radical prostatectomy (RARP) and extended pelvic lymphadenectomy. Pathological staging was pT2c R0 N0 (0/53 nodes), and postoperative PSA was undetectable. The patient remained free of recurrence for 5 years. In March 2023, a biochemical recurrence prompted repeated thoracoabdominal computed tomography (CT) and pelvic magnetic resonance imaging (MRI) scans; neither study included dedicated scrotal imaging, and both were negative for recurrence. By March 2024, serum PSA had increased to 5.6 ng/mL, coinciding with the onset of progressive, painless enlargement of the left testicle. Scrotal ultrasonography revealed a solid mass replacing the left testicular parenchyma. 18F-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) and choline PET/CT showed a hypermetabolic lesion confined to the left testis, with no evidence of extratesticular disease. The patient underwent left inguinal orchiectomy. Histopathological examination revealed metastatic adenocarcinoma with papillary architecture, morphologically consistent with ductal prostate origin. PSA levels declined rapidly postoperatively, reaching 0.07 ng/mL within 40 days. At 13-month follow-up, the patient remained clinically and biochemically free of disease without further treatment. This case represents one of the few documented instances of solitary testicular metastasis from PDA. It underscores the importance of continued PSA monitoring and highlights that isolated testicular involvement, whereas rare, may confer a more favorable prognosis than typically expected in metastatic PDA. In selected cases, orchiectomy may serve both diagnostic and therapeutic roles, supporting a conservative postoperative approach.