MALT lymphoma involving the kidney : A report of 10 cases and review of the literature

Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) can arise at any anatomic site, but involvement of the kidney is rare. We describe 10 cases of kidney MALT lymphoma, including 6 localized cases. No predisposing inflammatory conditions were identified, with the possible exception of coexistent renal Actinomyces infection in 1 case. We performed fluorescence in situ hybridization (FISH) using a malt1 break-apart probe in 7 cases. A malt1 gene rearrangement was identified in 1 case (14%). This case was further assessed by FISH using an IgH breakapart probe that showed IgH gene rearrangement. These results are suggestive of the t(14;18) involving malt1 and IgH. Immunostaining for NF-kappaB p65 showed nuclear positivity, consistent with NF-kappaB activation, in 3 of 5 cases assessed. Our results indicate that kidney MALT lymphomas share similarities with MALT lymphomas arising at other sites in that MALT lymphoma-associated translocations and NF-kappaB activation occur in a subset of cases.