[PRIMARY EFFUSION LYMPHOMA]. The lymphoma cells are large with immunoblastic, plasmablastic, or anaplastic morphology. The tumor cells may be so anaplastic mimicking anaplastic carcinomas (as in this case) and sarcomas metastatic to pleura. In all cases immunohistochemistry is required for final diagnosis which shows positivity for CD45 and HHV8 LANA antigen. The B-cell markers CD19, CD20, and CD79 can be negative. Surface immunoglobulin light chains are usually lacking but gene rearrangement study shows IgH rearrangement.