Solitary Testicular Metastasis as the Only Site of Recurrence in Prostate Adenocarcinoma

Prostate cancer preferentially metastasizes to bone and lymph nodes. Testicular metastases are exceptionally rare and are typically observed in the setting of advanced polymetastatic disease. Their presentation as an isolated oligometastatic relapse remains highly unusual. We report the case of a 76-year-old patient followed since 2019 for de novo metastatic prostate adenocarcinoma, initially treated with androgen deprivation therapy (ADT) with a complete response, who presented in March 2026 with a left testicular mass. Germ cell tumor markers were negative, while prostate-specific antigen (PSA) was elevated at 30 ng/mL. Prostate-specific membrane antigen positron emission tomography-computed tomography (PSMA PET-CT) demonstrated increased uptake involving both the testis and the peri-scrotal region. A radical inguinal orchiectomy was performed. Immunohistochemical analysis showed strong expression of prostein (P501S) and alpha-methylacyl-CoA racemase (AMACR), confirming the prostatic origin of the lesion. Postoperatively, systemic treatment was intensified using combined androgen deprivation therapy with abiraterone acetate, resulting in a marked decline in PSA levels. Testicular dissemination of prostate adenocarcinoma may occur through retrograde venous or lymphatic pathways. Diagnosis relies on advanced molecular imaging and immunohistochemistry, particularly in cases with reduced PSA expression. This case highlights the relevance of a multimodal strategy in oligometastatic disease, combining metastasis-directed surgery and intensified systemic therapy.