Penile involvement associated with renal pelvic squamous cell carcinoma: a case report and mechanistic considerations

Background: Squamous cell carcinoma (SCC) of the renal pelvis is an uncommon malignancy, accounting for less than 1% of upper urinary tract tumors. Penile metastasis from renal pelvic SCC has not been documented. Case presentation: A 74-year-old man presented with a firm penile nodule. Magnetic resonance imaging (MRI) demonstrated an intracavernosal mass, while contrast-enhanced computed tomography (CT) revealed a large left renal pelvic tumor (89 mm) with hepatic and hilar lymph node metastases, without pelvic or inguinal lymphadenopathy. Histopathological examination of both the renal pelvic and penile lesions showed keratinizing SCC. Immunohistochemistry demonstrated diffuse p40 and p63 positivity with PAX8 and p16 negativity, supporting a urothelial tract origin rather than a primary penile carcinoma. Given the disseminated disease and rapid clinical deterioration, no systemic or surgical therapy was undertaken, and best supportive care was provided. Conclusion: This case constitutes, to our knowledge, the first reported instance of penile involvement most consistent with metastatic renal pelvic SCC. In patients with advanced upper urinary tract malignancy who develop penile lesions, secondary involvement should be considered. The absence of regional lymphadenopathy and the disseminated pattern suggest a hematogenous retrograde venous dissemination pathway.