[A Case of Primary Renal Malignant Lymphoma Initially Managed as Severe Pyelonephritis in a Patient Undergoing Hemodialysis].

A 75-year-old male undergoing hemodialysis because of diabetic nephropathy was referred to our hospital complaining of high fever and swelling of the left kidney. Our initial clinical diagnosis was severe pyelonephritis. He was initially treated with intravenous antibiotics and his clinical symptoms subsequently improved but only temporarily. The high fever soon recurred, accompanied by progressive thrombocytopenia. His general condition deteriorated despite conservative treatment. He then underwent nephrectomy of the left kidney. However, the thrombocytopenia persisted and his general condition did not improve. The pathological diagnosis was malignant lymphoma (non-Hodgkin's lymphoma, diffuse large B-cell type). He received chemotherapy, but his status rapidly deteriorated and he died 1.5 months after the operation. Primary renal malignant lymphoma is very rare, because the kidney lacks lymphatic tissue.