The lymphoma contains a prominent large cell lymphoid infiltrate showing atypical large cells with irregular nuclear contours, mature chromatin, and inconspicuous nucleoli. Small reactive lymphocytes and a few plasma cells are intermixed. Image

CD20 strongly positive Image

PAX5 (brown) and CD30 (red) shows positive Image

There is abundant clear cytoplasm in these large cells. They appear somewhat compartmentalized by collagen, a feature characteristic of primary mediastinal (thymic) large B cell lymphoma. Image