Reports on primary renal lymphoma are scarce in the urological literature, the most part of them are secondary on a lymphomatous infiltration of the kidneys. We report the case of a 77 year old man with an incidental mass on the kidney. After radiological studies (CT), we practise nephrectomy with a pathological result of a non-Hodgking B primary lymphoma. The patient present a IgM monoclonal gammapathy who need complementary treatment with chemotherapy. A literature review on currently recommended diagnostic and treatment practices in presented.