1. ¹Department of Pathology, Baylor College of Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, USA
2. ²Department of Hematopathology, The Methodist Hospital, University of Texas MD Anderson Cancer Center, Houston, TX, USA
3. ³Department of Hematopathology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
4. ⁴Department of Medicine, Baylor College of Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, USA
5. ⁵Department of Molecular Pathology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
6. ⁶Department of Pediatrics, Baylor College of Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, USA
7. ⁷Department of Molecular Virology and Microbiology, Baylor College of Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, USA

Correspondence: Dr C-C Chang, MD, PhD, Department of Hematopathology, The Methodist Hospital, 6565 Fannin, MS205, Houston, TX 77030, USA. E-mail: jeffchang@tmh.tmc.edu

Received 15 September 2004; Revised 27 October 2004; Accepted 27 October 2004; Published online 3 December 2004.

Abstract

Plasmablastic lymphoma is an aggressive neoplasm that shares many cytomorphologic and immunophenotypic features with plasmablastic plasma cell myeloma. However, plasmablastic lymphoma is listed in the World Health Organization (WHO) classification as a variant of diffuse large B-cell lymphoma. To characterize the relationship between plasmablastic lymphoma and plasmablastic plasma cell myeloma, we performed immunohistochemistry using a large panel of B-cell and plasma cell markers on nine cases of plasmablastic lymphoma and seven cases of plasmablastic plasma cell myeloma with and without HIV/AIDS. The expression profiles of the tumor suppressor genes p53, p16, and p27, and the presence of Epstein–Barr virus (EBV) and human herpes virus type 8 (HHV-8) were also analyzed. All cases of plasmablastic lymphoma and plasmablastic plasma cell myeloma were positive for MUM1/IRF4, CD138, and CD38, and negative for CD20, corresponding to a plasma cell immunophenotype. PAX-5 and BCL-6 were weakly positive in 2/9 and 1/5 plasmablastic lymphomas, and negative in all plasmablastic plasma cell myelomas. Three markers that are often aberrantly expressed in cases of plasma cell myelomas, CD56, CD4 and CD10, were positive in 5/9, 2/5, and 6/9 plasmablastic lymphomas, and in 3/7, 1/5, and 2/7 plasmablastic plasma cell myelomas. A high Ki-67 proliferation index, overexpression of p53, and loss of expression of p16 and p27 were present in both tumors. No evidence of HHV-8 infection was detected in either neoplasm. The only significant difference between plasmablastic lymphoma and plasma cell myeloma was the presence of EBV-encoded RNA, which was positive in all plasmablastic lymphoma cases tested and negative in all plasma cell myelomas. In conclusion, most cases of AIDS-related plasmablastic lymphoma have an immunophenotype and tumor suppressor gene expression profile virtually identical to plasmablastic plasma cell myeloma, and unlike diffuse large B-cell lymphoma. These results do not support the suggestion in the WHO classification that plasmablastic lymphoma is a variant of diffuse large B-cell lymphoma.