Can melanoma metastasize to the kidney?

Can Melanoma Metastasize to the Kidney?

Yes, melanoma can metastasize to the kidney, though this is relatively uncommon compared to other metastatic sites. 1, 2, 3

Patterns of Renal Involvement

Melanoma can involve the kidney through several distinct mechanisms:

Metastatic Disease to Kidney Parenchyma

• Melanoma metastases to the kidney typically present as renal masses that may be detected on staging imaging (CT, PET/CT, or MRI) performed during initial melanoma workup or follow-up surveillance. 4, 1
• These metastases most commonly appear as tubulointerstitial masses, similar to other metastatic tumors to the kidney. 2
• The kidney is among the documented sites of distant metastatic disease in stage IV melanoma, where the site of metastasis serves as the most significant predictor of outcome. 4

Rare Intraglomerular Metastases

• Intraglomerular melanoma metastases represent an exceptionally rare pattern that can cause rapidly progressive kidney failure with proteinuria, hematuria, and dysmorphic red blood cells. 2
• This presentation mimics rapidly progressive glomerulonephritis and requires kidney biopsy for diagnosis, as imaging techniques have significant limitations in detecting intraglomerular disease. 2
• Melanoma cells can invade glomerular capillaries and even extend into proximal convoluted tubules, causing crescentic proliferation. 2

Ureteral Involvement

• Melanoma can metastasize to the ureters, causing obstruction and hydronephroureter, though this is extremely rare. 5
• Ureteral metastases may present with filling defects on retrograde pyelography and can be clinically silent until causing significant obstruction. 5

Clinical Implications and Diagnostic Approach

Critical Diagnostic Pitfall

The most important clinical consideration is that a renal mass in a patient with melanoma history may represent either metastatic melanoma OR a concurrent primary renal cell carcinoma. 1

• Biopsy of any renal mass is essential in melanoma patients to establish the correct diagnosis and guide optimal treatment, as the two entities require completely different management strategies. 1
• Studies have documented cases where renal masses detected during melanoma staging investigations proved to be separate primary renal cell carcinomas rather than metastases. 1
• This association is not coincidental—patients with malignant melanoma have an increased risk of developing renal cell carcinoma as a second primary malignancy. 1

Timing Considerations

• Renal metastases can occur many years after initial melanoma diagnosis, with documented cases appearing 8-20 years after the primary melanoma was treated. 1, 3
• Even patients with thin melanomas or those considered in remission can develop late renal metastases. 1, 2
• Ocular melanoma has particular propensity for late renal metastases, with cases documented two decades after enucleation. 3

Staging and Surveillance

• Routine imaging (CT scan, PET/CT, MRI) is recommended only to evaluate specific signs or symptoms in early-stage melanoma patients (stages IB-II), not for routine surveillance. 4
• For stage III disease with positive sentinel nodes or clinically positive nodes, baseline imaging for staging should be considered (category 2B recommendation), which may detect concurrent renal involvement. 4
• Stage IV melanoma patients require comprehensive imaging including chest, abdominal/pelvic CT, and brain MRI as clinically indicated to identify all sites of metastatic disease, including potential renal involvement. 4

Prognostic Significance

• When melanoma metastasizes to the kidney as part of stage IV disease, the site of metastasis becomes the most significant predictor of outcome, along with elevated lactate dehydrogenase (LDH). 4
• Long-term survival in patients with distant metastatic melanoma is generally less than 10%, though outcomes vary based on specific metastatic sites and disease burden. 4

Key Clinical Pearls

• Always biopsy renal masses in melanoma patients—never assume they represent metastases without histologic confirmation. 1
• Maintain high index of suspicion for renal involvement even decades after melanoma treatment, particularly with ocular melanoma. 3
• Consider kidney biopsy in melanoma patients presenting with rapidly progressive renal failure and active urinary sediment, as intraglomerular metastases may not be visible on imaging. 2
• Document all sites of metastatic disease and serum LDH at diagnosis of stage IV disease for accurate prognostication. 4