THE DETECTION OF ACQUIRED-IMMUNODEFICIENCY-SYNDROME ASSOCIATED KAPOSI-SARCOMA CELLS IN PLEURAL EFFUSION BY CD34 IMMUNOSTAIN

Background. Acquired immunodeficiency syndrome (AIDS)-associated Kaposi sarcoma (KS) cells have not been reported in pleural effusions. This study identifies the effusional form of AIDS-KS cells with the CD34 antibody, a newly recognized marker for vascular neoplasia. Methods. In the pleural effusion of a patient with AIDS and biopsy proven pulmonary KS, the authors found bizarre amoeboid cells. Parallel sections from the cell blocks of the pleural effusions from the index patient and six other patients with AIDS were immunostained for cytokeratin, CD68, leukocyte common antigen (LCA), Factor VIII:R, and CD34. Results. The atypical cells were not observed in the pleural effusions of the other six patients with AIDS. The atypical cells were positive for CD34 (4+) and Factor VIII:R (1+) but were negative for cytokeratin, CD68, or LCA, which were expressed by mesothelial cells, macrophages, and lymphocytes, respectively. The expression for CD34 and Factor VIII:R was limited to a sharply delineated perinuclear region in the cytoplasm, corresponding to the erythrocyte-containing intracytoplasmic space of the atypical cells on the filter. Conclusion. In conclusion, the erythrocyte-containing intracytoplasmic space within the atypical cells most likely represents the intracytoplasmic lumina of the AIDS-KS endothelial cells and the CD-34-positive atypical cells represent the effusional form of the AIDS-KS cells.