Case report: intraglomerular metastasis with neoplastic cell interposition

Severe Acute Kidney Injury Due to Intraglomerular Melanoma: A Case Report

Metastatic disease in the kidney is relatively uncommon compared to other body sites. In most cases it presents as an unilateral and unifocal mass in the tubulointerstitial region. Intraglomerular metastases are even rarer, and their diagnosis is hampered by the limitation of imaging techniques to detect them. We describe the finding of intraglomerular metastases in a patient affected by a malignant melanoma considered to be in partial remission, with no evidence of melanoma progression on the previously performed computed tomography (CT) scan. This patient developed rapidly progressive kidney, failure, proteinuria and hematuria with dysmorphic red blood cells in the urine sediment. Kidney biopsy showed a marked crescentic proliferation caused by tumor cells, which even invaded the proximal convoluted tubule. Melanoma cells were also found in the lumina of the glomerular capillaries, distending their basement membranes. Our case describes the histologic and electron microscopic findings of this form of intraglomerular metastasis and reminds us of its inclusion in the differential diagnosis of rapidly progressive kidney failure.

Intraglomerular micrometastasis of squamous cell carcinoma

Intraglomerular metastasis is a rare manifestation of disseminated malignancies. We present here a case of intraglomerular metastatic carcinoma diagnosed as an incidental finding on a kidney biopsy in a 62-year-old male presenting with acute renal failure and metastatic penile squamous cell carcinoma. A proliferative lesion composed of highly atypical epithelial cells was found within a capillary loop and adjacent urinary space of an isolated glomerulus, which was immunoreactive for markers of squamous cell carcinoma. This case is a reminder that circulating cancer cells can occasionally lodge in glomeruli and appear as micrometastasis in kidney biopsies performed for the evaluation of renal dysfunction.

Intraglomerular crescentic metastases of malignant melanoma

We describe here a patient with a metastatic malignant melanoma displaying crescentic lesions in the glomeruli. A 64-year-old woman was referred to our hospital because of a sudden increase of serum creatinine. Clinical diagnosis suggested rapidly progressive glomerulonephritis. Renal biopsy revealed diffuse crescentic lesions containing metastatic melanoma cells. These cells were also seen in the glomerular capillary lumina and tubules, and a few scattered tumor cells were also present in the interstitium. Glomerular metastasis is a very rare entity. To the best of our knowledge, this patient is the first to be described in the English language literature showing intraglomerular metastasis of malignant melanoma as demonstrated by needle biopsy and is only the second patient with intraglomerular metastasis presenting with acute renal failure.

Paraneoplastic glomerular diseases and malignancies

Paraneoplastic glomerulopathies are rare manifestations of neoplastic disease to be distinguished from iatrogenic renal damage. Solid tumors are preferentially associated with membranous nephropathy, whereas Hodgkin's lymphomas are associated with minimal change disease. The most common neoplasia associated with paraneoplastic glomerular disease are carcinomas of the lung and of the gastrointestinal tract. Nephrotic syndrome is the most frequent presentation of paraneoplastic glomerulopathy and the most critical glomerular disease regarding prognosis and patient care. Renal biopsy is recommended in patients with glomerular proteinuria or nephrotic syndrome and cancer, depending on life expectancy and therapeutic options. The primary treatment must be directed at the cancer in all cases. Symptomatic treatment of the nephrotic syndrome with diuretics and ACE inhibitors is justified. Prevention of nephrotic syndrome complications, i.e. thromboses and infections, should also be addressed and systematic regular renal follow-up is warranted. All treatments should be regularly reviewed to avoid toxicity, associated renal function loss or low albumin levels for patients receiving albumin-binding drugs. Epidemiologic studies have low evidence-based value. There is no widely accepted experimental model of the association of glomerulopathy and cancer. Thus, epidemiologic and mechanistic studies are needed to determine the true prevalence of paraneoplastic glomerulopathies and investigate new pathophysiologic approaches.