Primary renal lymphoma: report of four cases.

Background: Although secondary renal involvement from systemic lymphoma is very frequent, primary renal lymphoma is a rare entity. It is characterized by aggressive histopathology, very early extra-renal infiltration and poor prognosis.
Case Reports: Here, we report 4 cases of primary renal lymphoma presenting with unilateral renal masses, which after radiological and clinical examination were assumed to be renal cell carcinoma. 3 patients were diagnosed with Non-Hodgkin's lymphoma by nephrectomy and one patient was diagnosed by open renal biopsy. Histopathological subtypes were diffuse large B cell lymphoma in 2 cases and non-Hodgkin's lymphoma of small B cell type in the others. While 3 of the patients were treated with systemic chemotherapy, the fourth patient refused chemotherapy. 2 patients (no. 2 and 3) were still in complete remission and were followed regularly in the second and first year after diagnosis, respectively.
Conclusions: Since it is difficult to diagnose primary renal lymphoma, most patients with this kind of tumor undergo radical nephrectomy, and diagnosis of primary renal lymphoma is delayed. The authors believe that both the delayed diagnosis due to anatomical difficulties and the histological aggressive characteristics of this disease are equally responsible for the poor outcome in the case of primary renal lymphoma.
(Copyright 2009 S. Karger AG, Basel.)