API2-MALT1 Fusion Defines a Distinctive Clinicopathologic Subtype in Pulmonary Extranodal Marginal Zone B-Cell Lymphoma of Mucosa-Associated Lymphoid Tissue

摘要

t(11;18)(q21;q21) is associated with mucosa-associated lymphoid tissue (MALT)-type lymphoma and results in >API2-MALT1 fusion. However, its clinicopathologic significance remains unclarified. >API2-MALT1 fusion is detected most frequently in MALT lymphomas primarily involving the lung. We therefore screened 51 cases of pulmonary MALT lymphoma for >API2-MALT1 fusion, and studied its relationship with clinicopathologic factors including the immunohistochemical expression of BCL10, another MALT lymphoma-associated molecule. The >API2-MALT1 fusion transcript was detected in 21 of 51 (41%) cases, and was correlated with the absence of any underlying autoimmune disease, and with a normal serum lactate dehydrogenase, a “typical” histology without marked plasmacytic differentiation or an increased number of large cells, and aberrant nuclear BCL10 expression. However, its prognostic impact was not identified in the limited follow-up (6 to 187 months, median 27). These data suggest that the >API2-MALT1 fusion may be a causative gene abnormality unrelated to autoimmune disease. In addition, this alteration may define a homogeneous MALT lymphoma subtype that is clinically more indolent and histologically more “typical.” Aberrant nuclear BCL10 expression may have a possible role as a tool to screen for this >API2-MALT1 fusion. A large-scale study with a long follow-up is necessary to establish the prognostic significance of >API2-MALT1 fusion.