Coexisting thymic and gastric lymphomas of mucosa-associated lymphoid tissues in a patient with Sjogren syndrome

Lymphomas of mucosa-associated lymphoid tissues (MALTomas) arising from the thymus are extremely rare. In this case report, we describe a 36-year-old woman with an 11-year history of Sjogren syndrome who was found to have a t hymic MALToma coexisting with a gastric MALToma. Both tumors shared similar histologic features, showing clusters of centrocytic-like B cells, lymphoe pithelial lesions, and prominent plasmacytic differentiation. They also sho wed the following identical immunohistochemical features: CD20(+), IgA/lamb da(+), CD5(-), and CD43(-). Molecular studies using polymerase chain reacti on methods revealed monoclonal gene rearrangement of the immunoglobulin hea vy chain in the gastric MALToma, but not in the thymic MALToma. The possibl e pathogenesis of this unusual case is discussed.