Two cases of MALT lymphoma that developed in the setting of autoimmune disorders and carried the t(X;14)(p11;q32)/GPR34-IGH translocation

Abstract

Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type (MALT lymphoma) frequently occurs in the stomach, but can also arise in epithelial tissues/organs other than the gastrointestinal tract, often in the setting of long-lasting antigenic stimulation due to chronic bacterial infections or autoimmune disorders. Recurrent chromosomal translocations in MALT lymphoma have been identified. The first patient (case 1) was a 66-year-old female who presented with a left parotid gland tumor. She had been diagnosed with Sjögren syndrome and immune thrombocytopenia. Seven years after surgical resection, she relapsed involving the palatine tonsil and ileocecum. She then received R-CHOP chemotherapy, leading to complete resolution of the tumor. The second patient (case 2) was a 66-year old male who presented with symmetric enlargement of the bilateral parotid glands. He had been treated for rheumatoid arthritis with prednisolone and methotrexate followed by intravenous tocilizumab. He was treated with R-CHOP, and achieved complete response. Pathological specimens from both cases revealed salivary gland tissues diffusely infiltrated by CD20⁺ lymphoma cells, which generated the lymphoepithelial appearance. Lymphoma cells were medium to large in size, with cytomorphological features of diffuse large B-cell lymphoma (DLBCL). The cells were CD5⁻, CD10⁻, CD19⁺ , CD21⁻, CD22⁺ , and CD23⁻, and expressed surface immunoglobulin µδ/κ. G-banding and FISH demonstrated t(X;14)(p11;q32) in both cases. The breakpoints were localized at intron 1 (case 1) and coding exon 3 of GPR82 (case 2), which is located 27-kb downstream of GPR34, and breakpoints in IGH were within the switch region associated with IGH Cα2. These two cases were characterized by three factors; background of long-lasting autoantigenic stimulation, the t(X;14)(p11;q32) translocation, and intermediate features between low-grade MALT lymphoma and DLBCL on both cytomorphology and clinical behavior. This translocation results in high GPR34 expression and is considered to be involved in tumorigenesis.