Plasmablastic lymphoma is a rare and aggressive B cell lymphoma that is considered to be strongly associated with HIV infection. This article explores the histological morphology and immunohistochemical characteristics of HIV/AIDS-related plasmablastic lymphoma with the goal of improving the diagnosis and treatment of this rare tumor. According to criteria of the World Health Organization Classification of Tumors of Hematopoietic and Lymphoid Tissues (2008), six plasmablastic lymphoma cases admitted to the Shanghai Public Health Clinical Center were comprehensively analyzed with conventional hematoxylin-eosin staining, immunohistochemical staining and in situ hybridization. The morphological features of six tumors were consistent with PBL. Immunohistochemical staining showed that all six cases were negative for CD19, CD20, and CD79a, and positive for OCT-2, BOB-1, VS38c, and melanoma ubiquitous mutated 1. The Ki67 proliferation index was higher than 90% in all six cases. In situ hybridization indicated that four cases were EBER-positive. In addition, three cases had C-MYC translocation rearrangement. Our results showed that the immunophenotypes of PBL vary, which makes PBL diagnosis difficult. Therefore, morphological characteristics, immunophenotypic markers, and clinical data should be used in combination to enable an accurate diagnosis, especially in the presence of immunophenotypic variation, as this approach will facilitate timely treatment.