Renal small B-cell lymphoma with plasmacytic differentiation presenting with monoclonal gammopathy and disseminated intravascular coagulation syndrome

Primary renal lymphomas are very rare. However, the kidney may be a site of metastasis, usually from a disseminated aggressive lymphoma. A 58-year-old woman was brought to the medical facility due to acute mental confusion, severe hypotension, septic shock, and signs of disseminated intravascular coagulation. Laboratory tests showed severe leukopenia, renal failure, altered liver function, and elevated serum lactate dehydrogenase levels. Protein electrophoresis revealed hypergammaglobulinemia with a monoclonal peak of IgG lambda. The clinical outcome was fulminant and the patient died less than 24 hours after admission. Autopsy revealed an indolent B-cell lymphoma with extensive plasmacytic differentiation infiltrating the right renal sinus and involving the submandibular and sublingual glands, cervical and peri-aortic lymph nodes, multiple microscopic foci in pituitary and adrenal glands, lung, breast, liver, thyroid, and bone marrow. Numerous IgG4-positive plasma cells were detected by immunohistochemistry although other histological features of IgG4-related disease were missing. There was also extensive hemorrhagic necrosis of the adrenal glands and purulent cystitis, which was probably responsible for the septic shock. The authors concluded that the kidney was most likely the primary site of the indolent lymphoma, as that was the site with the largest tumor mass. Infiltration of other organs was considered as dissemination of the disease. The differential diagnosis with mucosa-associated lymphoid tissue and lymphoplasmacytic lymphoma is discussed.