T(14;18)(q32;q21) involving MALT1 and IGH genes in an extranodal diffuse large B-cell lymphoma.

Two translocations involving the MALT1 gene have been described in extranodal marginal zone B-cell lymphomas of MALT type. A t(11;18)(q21;q21) involving API2 and MALT1 occurs in a subset of MALT lymphomas but with only rare exception is absent in diffuse large B-cell lymphomas (DLBCL), even at MALT sites. More recently, a t(14;18)(q32;q21) involving IGH and MALT1 has been described in nongastric extranodal MALT lymphomas. This translocation is indistinguishable from the IGH-BCL2 translocation by using classical cytogenetics. We report the IGH-MALT1 translocation in a cutaneous DLBCL as shown by classical cytogenetics and molecular cytogenetic analysis. This is the first report of an IGH-MALT1 translocation in DLBCL. These findings indicate that MALT1 translocations are not restricted to indolent-appearing lymphomas, provide further evidence that API2-MALT1 and IGH-MALT1 translocations exhibit biologic differences, have implications regarding the pathogenesis of some extranodal DLBCL, and emphasize that a t(14;18)(q32;q21) cannot be assumed to reflect a BCL2 translocation.