Mucosa-associated lymphoid tissue (MALT) lymphoma develops in the context of longstanding antigenic stimulation such as infection with Helicobacter pylori or autoimmune disease, including Sjögren's syndrome (SS). Recently, two chromosomal aberrations involving the MALT1 gene, i.e., t(11;18)(q21;q21) and t(14;18)(q32;q21) have been reported as genetic events specific for MALT lymphoma. In view of the association between SS and the development of MALT lymphoma, we have analyzed the frequency of t(11;18)(q21;q21) and t(14;18)(q32;q21) in patients with MALT lymphomas arising in the background of SS.
A retrospective analysis of patients diagnosed with MALT lymphoma and SS was performed. The t(11;18)(q21;q21) was analyzed using reverse transcriptase-PCR, whereas t(14;18)(q32;q21) was assessed by two-color interphase fluorescence in situ hybridization.
Twenty-six patients (20 female and 6 male) with MALT lymphoma and SS could be identified. The lymphoma was located in the parotid (n = 14), orbit (n = 2), and submandibular gland (n = 1), whereas 9 patients had gastric MALT lymphoma. Seven of 26 patients (27%) harbored t(11;18)(q21;q21). Interestingly, only 1 of 17 patients (6%) with extragastrointestinal lymphoma was positive, as opposed to 6 of 9 patients (67%) with gastric MALT lymphoma. Four of 26 patients were positive for t(14;18)(q32;q21): 3 of 17 extragastrointestinal (18%) and 1 of 9 gastric lymphomas (11%).
The overall frequency of MALT1 rearrangement appears to be low in patients with extragastrointestinal MALT lymphoma associated with SS. By contrast, MALT1 rearrangement was demonstrated in 7 of 9 patients (78%) with gastric MALT lymphoma and SS. This finding may explain at least in part why gastric MALT lymphomas in patients with SS are refractory to H. pylori eradication therapy.