Thymic marginal zone lymphoma of mucosa-associated lymphoid tissue

Abstract

Background and aim: Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) arising from the thymus is a rare disease; 43 cases have been described in the English literature. We describe the clinicopatholgic characteristics and molecular findings of six Korean cases of MALT lymphomas arising from the thymus. Methods: We assessed characteristic clinicopathologic findings and performed fluorescence in situ hybridization (FISH) using a MALT1 break-apart probe and immunohistochemical staining for immunoglobulin subtypes and bcl-10 protein. Results: These cases demonstrated a female predominance, autoimmune context, frequent cysts and prominent lymphoepithelial lesion formation, consistent plasma cell differentiation with predominantly IgA expression, and a lack of MALT1 rearrangement. However, systemic lupus erythematosus and rheumatoid arthritis were as prevalent as Sjögren syndrome in these Korean thymic MALT lymphoma patients, contrary to reports from other countries which described Sjögren syndrome as a predominant underlying disease. Conclusions: The reported Korean cases of thymic MALT lymphoma might have different autoimmune context although our series reconfirms other distinctive clinicopathologic and molecular characteristics of thymic MALT lymphomas.