Prostate cancer metastasis to the penis with low serum prostate specific antigen level: A case report

Introduction Metastasis of prostate cancer (PCa) to the penis is an extremely rare event, which brings substantial clinical challenges. Particularly in cases with low or undetectable serum PSA levels, it frequently leads to delayed diagnosis and management. Given the extreme rarity of this clinical presentation and the associated high risk of misdiagnosis, here we reports a case of penile metastasis secondary to prostate cancer, with the aim of improving clinical awareness of this rare condition and emphasizing that clinicians should maintain a high degree of clinical suspicion even in the absence of biochemical evidence of progression. Case Presentation We reported a case of patient, 76-year-old, who was diagnosed prostate adenocarcinoma and underwent combined androgen blockade (Bicalutamide+Goserelin) therapy for two years. The patient's serum PSA levels remained at a relatively low level, and no metastases were observed. Nevertheless, following laparoscopic radical prostatectomy (LRP), painful nodules were detected at the glans penis. Biopsy confirmed that the penile mass was a metastasis from prostate cancer. Subsequently, metastatic lesions were successively disseminated to the lungs, liver, and lymph nodes. The patient serum tPSA level increased rapidly, and showed no response to endocrine therapy after the development of multiorgan metastases. The patient died in August 2024, with an overall survival of 43 months from initial prostate cancer diagnosis in January 2021 and 12 months from penile metastasis diagnosis in August 2023, due to disease progression with multiple organ failure. Conclusions Penile metastases from prostate cancer should be considered in patients with a prior history of prostate malignancy who present with penile complaints, even when bone metastases are well-controlled and serum PSA levels remain low under hormonal therapy. Although penile metastasis is a rare event, it is more likely to occur in patients with high-grade, locally advanced prostate cancer, particularly when there are atypical clinical features. In addition to conventional PSA monitoring, a comprehensive physical examination and advanced imaging are recommended to facilitate early detection and guide appropriate management.