A rare case of penile metastasis from renal cell carcinoma following combination therapy with immune checkpoint and tyrosine-kinase inhibitors: A case report and literature review.

RATIONALE: Penile metastasis from renal cell carcinoma (RCC) is an extremely rare clinical entity, particularly in the era of immune-checkpoint inhibitor and tyrosine-kinase inhibitor combination therapy. The mechanisms, clinical presentation, and optimal management of such cases remain poorly understood.

PATIENT CONCERNS: A 75-year-old man with metastatic RCC undergoing systemic therapy developed persistent, painful erections (malignant priapism), along with urinary retention, general malaise, and back pain, 2 years after initiating treatment.

DIAGNOSIS: Magnetic resonance imaging of the penis revealed a hypointense lesion on T2-weighted imaging and restricted diffusion on diffusion-weighted imaging, suggestive of tumor infiltration into the corpus cavernosum. Blood gas analysis from corporal aspiration was consistent with nonischemic priapism. A diagnosis of penile metastasis from RCC was established.

INTERVENTIONS: Embolization of the common penile artery was performed, followed by palliative radiotherapy (30 gray in 10 fractions).

OUTCOMES: Despite these interventions, penile rigidity persisted, though partial symptomatic relief and pain reduction were achieved. Disease progression was noted, and the patient died approximately 3 months after the diagnosis of penile metastasis.

LESSONS: This is the first reported case of penile metastasis from RCC during immune-checkpoint inhibitor-tyrosine-kinase inhibitor therapy, highlighting a rare but clinically important metastatic pattern potentially unmasked by prolonged survival. Retrograde dissemination via Batson venous plexus may underlie this presentation. Radiotherapy and embolization may offer partial symptomatic relief, but the prognosis remains poor. Accumulation of further cases is necessary to guide future management strategies.