[Renal infiltrate by a plasmocytoïd chronic B lymphocytic leukaemia and renal failure: a rare occurrence in nephropathology. A case report and review of the literature].

We report the case of a 55-year-old male with renal failure as the initial manifestation of interstitial and focal infiltration of the kidneys by a small B-cell lymphoma. Since three years, this patient had a history of CLL with plasmocytic differentiation and was left untreated owing to stade A Binet classification. After chemotherapy, the lymphocytosis and the adenopathies disappear and the renal function improve. Infiltration of the kidneys by non-Hodgkin small B-cell lymphoma, including chronic lymphocytic leukaemia (CLL), is usually asymptomatic, fortuitously discovered at the time of an X-ray examination or at autopsy. Association with renal failure is extremely rare. We review the reported cases of renal failure associated with lymphomatous infiltration (13 cases of CLL and five cases of lymphoplasmocytic lymphoma kappa or lambda IgM), with the following conclusions: in most cases, renal insufficiency appears in a few months and significantly disappears after chemotherapy; the renal infiltrate is usually focal in lymphoplasmocytic lymphoma and rather massive and diffuse in CLL; the neoplastic feature of a small B-cell lymphoïd infiltrate may be difficult to determine: a poorly limited, monomorphous, CD20+ CD5+ lymphoid infiltrate is lymphomatous. In case of plasmocytic differentiation, it must be looked for kappa or lambda monotypy; the type of the lymphomatous infiltrate according to the WHO 2008 classification may be difficult to determine in a small sampling of renal tissue: the renal infiltrate must be compared, if possible, with a lymph node infiltrate. Owing to its bad prognosis, mantle cell lymphoma must be distinguished from other small B-cell lymphoma like CLL/small lymphocytic lymphoma, marginal zone lymphoma and lymphoplasmocytic lymphoma.