LYMPHOMA OF THE MUCOSA-ASSOCIATED LYMPHOID-TISSUE OF THE LUNG - A MULTIFOCAL CASE OF COMMON CLONAL ORIGIN

Low-grade B-cell lymphomas of the mucosa-associated lymphoid tissue (M ALT) are extranodal tumors that tend to be localized. In this case rep ort, the authors describe an unusual multifocal pulmonary MALT lymphom a, which presented radiologically as three discrete lesions involving two separate lobes of the lung, in addition to numerous separate macro scopic and microscopic foci of disease. The lesions were composed of c entrocyte-like cells and cytologically bland plasma cells surrounding reactive lymphoid follicles with focal areas resembling lymphoid inter stitial pneumonia (LIP). Immunohistochemical studies demonstrated a pr edominance of immunoglobulin kappa light chain positive plasma cells i n the largest lesion. A polymerase chain reaction (PCR) assay demonstr ated conserved immunoglobulin heavy chain gene rearrangements in the l arge tumor nodules as well as microscopic foci resembling LIP. This ca se illustrates the utility of PCR for identifying the clonal nature of lymphoid lesions that are too small or heterogeneous to unequivocally assess by other means.