Secondary pleural involvement by an AIDS-related anaplastic large cell (CD30+) lymphoma simulating metastatic...

We report a patient with acquired immunodeficiency syndrome with secondary pleural and pulmonary involvement by a CD30+ anaplastic large cell lymphoma (ALCL) that morphologically simulated metastatic adenocarcinoma. We describe the morphologic findings in order to heighten awareness that CD30+ ALCL may mimic metastatic adenocarcinoma in a body fluid or bronchial brushing and should be considered in the differential diagnosis. Primary body cavity based (PCBC) AIDS-related lymphoma is a relatively newly described disease entity with morphologic features bridging ALCL and large cell immunoblastic lymphoma with a CD30+ null immunophenotype. A morphology mimicking adenocarcinoma has not been previously described in this entity but should be considered in a patient with AIDS presenting exclusively with a serous effusion. Appropriate immunoperoxidase staining should aid in these differential diagnoses.