Detection of t(11;18)(q21;q21) by multiplex RT-PCR of the API2-MALT1 fusion transcript. Blots from top to bottom: second PCR-A, second PCR-B, second PCR-C, and beta-actin mRNA amplification. Lane N, negative control (normal lymph node). Lanes 1 to 12, H pylori–independent MALT lymphomas (positive). Lane 13, H pylori–dependent MALT lymphoma (positive). Lanes 14 to 16, H pylori–dependent MALT lymphomas (negative).