Renal cell carcinoma presenting as nephrotic syndrome

Area of Science:

• Nephrology
• Oncology
• Pathology

Background:

• Nephrotic syndrome is characterized by heavy proteinuria, edema, and renal impairment.
• Renal cell carcinoma (RCC) is a malignancy of the kidney, rarely associated with paraneoplastic syndromes.
• Minimal-change nephropathy (MCN) is a common cause of nephrotic syndrome in children, typically idiopathic.

Observation:

• A 64-year-old woman presented with significant edema and laboratory findings indicative of nephrotic syndrome (20.7 g urinary protein/24h) and renal impairment (serum creatinine 197 µmol/l).
• Imaging revealed a renal tumor, later confirmed as renal cell carcinoma extending to the renal vein margin post-nephrectomy.
• Histopathological examination of non-tumorous kidney tissue showed normal light microscopy but electron microscopy revealed podocyte foot process fusion, consistent with MCN.

Findings:

• The case presents a rare association between renal cell carcinoma and nephrotic syndrome.
• The underlying cause of nephrotic syndrome was identified as minimal-change nephropathy, which is highly unusual in the context of a solid tumor.
• This suggests a potential paraneoplastic mechanism linking the renal tumor to glomerular podocyte injury.

Implications:

• This case highlights the importance of considering paraneoplastic syndromes in patients with unexplained nephrotic syndrome, even in the presence of solid tumors.
• Further research into the mechanisms underlying paraneoplastic MCN associated with RCC may reveal novel therapeutic targets.
• Clinicians should maintain a high index of suspicion for MCN in patients with RCC and nephrotic-range proteinuria.