Renal intravascular large B-cell lymphoma localized only within peritubular capillaries. Report of a case.

We report a 35-year-old Japanese woman with intravascular large B-cell lymphoma diagnosed by percutaneous renal biopsy. The patient was referred to our institution for further examination of fever of unknown origin. She had renal dysfunction with a creatinine clearance of 44.1 mL/min, and daily urinary excretion of 0.22 g of protein and 21.5 mg of beta 2 microglobulin. Computed tomography showed markedly enlarged kidneys bilaterally. Percutaneous renal biopsy showed that an island-like atypical lymphoid cell accumulation was encircled with the peritubular capillary walls in many areas of the tubulo-interstitium, resulting in marked destruction of tubular structure. However, almost all the glomeruli were intact. Immunohistochemical analysis confirmed the diagnosis of intravascular large B-cell lymphoma. Shortly after diagnosis, she was treated with rituximab, cyclophosphamide, hydroxydaunomycin, oncovin, and prednisolone, and her renal function and size improved. Renal involvement by lymphoma has been classified into two categories: intraglomerular intravascular lymphoma and tubulointerstitial diffuse invasion type that is distinct from intravascular lymphoma. For the latter cases with renal dysfunction and marked bilateral nephromegaly but without proteinuria, intravascular lymphoma within intra-peritublar capillaries should be considered as a possible diagnosis.