Mucosa-associated lymphoid tissue lymphoma involving the kidney: a case report and review of the literature.

Mucosa-associated lymphoid tissue (MALT) lymphomas arise from various anatomic sites, mostly observed in the gastrointestinal tract; however, involvement of the kidney is extremely rare. We report a case of MALT lymphoma involving the kidney in a 70-year-old man. Radical nephrectomy was performed under the diagnosis of renal cell carcinoma preoperatively. However, the renal specimen showed that the diffuse small- to medium-sized lymphocytes were scattered and formed colonies, and the neoplastic lymphoid cells were positive for CD20, CD79α, and Bcl-2, but negative for CD10 and Cyclin D1; therefore, the final histological diagnosis was MALT lymphoma involving the renal pelvis. Although he was referred to the department of hematology, no additional treatment was given postoperatively, and he has survived for 4 months without evidence of a recurrence of lymphoma at the last follow-up. To the best of our knowledge, to date 37 reports of MALT lymphoma involving the kidney have been published in the literature. We report a case of MALT lymphoma involving the kidney, and review the existing literature.