Malignant lymphoma of the kidney mimicking rapid progressive glomerulonephritis.

Primary renal lymphoma (PRL) is rare and often presents as rapidly progressive renal failure. Most cases of PRL are large-cell lymphomas of B-cell lineage. Herein, we report a 75-year-old female patient with infiltrative CD20 (+) B-cell lymphoma who underwent 4 consecutive courses of chemotherapy with R-CVP (rituximab, cyclophosphamide, vincristine, and prednisone) and after 12 sessions became free from hemodialysis in good general condition. Her serum creatinine level gradually decreased to 4.1 mg/dl with adequate urine output. Unfortunately, a relapse of CD20 (-) lymphoma developed rapidly involving other organs. She died with severe hospital-acquired pneumonia and febrile neutropenia after the last chemotherapy with R-MINE almost 1 year after onset of symptoms. We conclude that renal biopsy enables prompt diagnosis in rapidly progressive renal failure and immunophenotyping and also staging workup of the lymphoma in case of positive biopsy. Though rituximab improved response rate of PRL, it reduced expression of CD20. This may relate to frequent relapse/resistance after rituximab therapy and poor long-term patient survival.