Microscopic examination of involved PBD masses and infiltrates generally reveals diffuse proliferations of immunoblast-like cells with prominent features of plasma cells, i.e.<unk>  cells. Immunostaining of these cells indicate that they lack B-cell marker proteins (e.g. CD20 and PAX5 in ~10% of cases CD20 may be expressed at very low levels) but rather express plasma cell marker proteins (e.g. CD38, CD138, IR4/MUM1, XBP1, IL21R, and/or PRDM1). The abnormalities in gene structures and expressions reported in the Pathophysiology section, particularly rearrangement and/or over expression of the MYC proto-oncogene, may also be apparent in these cells. The presence of HIV/AIDS or other causes of immuno-incompetence (see previous section), a history of having a low-grade<unk> , and/or the presence of EVB+ plasmablasts in the disease's lesions would support the diagnosis of<unk> . Differential diagnosis Various<unk> s can exhibit the microscopic appearance, including<unk>  cells, and presentation of<unk> . These<unk> s can usually be differentiated from<unk>  by further examinations of the plasmablasts for various marker proteins and determining other factors that favor the diagnosis of these<unk> s rather than<unk> , as indicated in the following descriptions. Anaplastic<unk>  kinase-positive large B-cell<unk>  Unlike<unk> , the<unk>  cells in anaplastic<unk>  kinase-positive large B-cell<unk>  strongly express the product of the ACVRL1 gene, i.e. activin receptor-like kinase 1 (ALK1) and are not infected with EBV and therefore do not express this virus's EBER or BART RNAs. Human herpesvirus 8-positive diffuse large B-cell<unk> , not otherwise specified Unlike<unk> , the<unk>  cells in human herpesvirus 8-positive diffuse large B-cell<unk> , not otherwise specified express products of herpesvirus 8 (also termed Karposi sarcoma virus) such as LANA-1 protein. Also unlike<unk> , these<unk>  cells do not express CD30, CD138, CD79a, or a clonal IgM antibody and usually are not EBV-infected and therefore usually do not express this virus's EBER or BART RNAs. Primary effusion<unk>  In contrast to<unk> , the<unk>  cells in primary effusion<unk> s, whether HHV8-positive or HHV8-negative, usually strongly express CD45 and in HHV8 cases express HHV8 proteins such as the LANA-1 protein. Primary effusion<unk> , HH8-negative also differs from<unk>  in that its<unk>  cells frequently express certain B-cell marker proteins such as CD20 and CD79a.<unk>  plasma cell<unk>  Various factors distinguish<unk>  plasma cell<unk>  from<unk> . Prior diagnosis of plasma cell<unk>  (i.e. multiple myeloma or plasmacytoma), the presence of lytic bone lesions, increased levels of serum calcium, renal insufficiency, and anemia, and the presence of a myeloma protein in the serum and/or urine favor the diagnosis of<unk>  plasma cell<unk>  rather than<unk> . Ultimately, however, the marker proteins expressed by the<unk>  cells in the two diseases are almost identical and a diagnosis of<unk>  neoplasm, consistent with<unk>  or multiple myeloma" may be acceptable in some cases according to the current World Health Organization classification. Other B-cell<unk> s ==== The<unk>  cells in B-cell<unk> s, including diffuse B-cell<unk> s, chronic lymphocytic leukemia/small lymphocytic<unk> , and follicular<unk>  generally express CD20 and often express CD45 marker proteins. While<unk><unk>  cells weakly express CD20 in 10% of cases, the strong expression of CD20 and the expression of CD45 virtually rules out<unk> .
Plasmablastic lymphoma
Diffuse large B-cell lymphoma
Mixed-cell lymphoma
Marginal zone B-cell lymphoma
Aggressive lymphoma
Gray zone lymphoma
Follicular lymphoma
Anaplastic large-cell lymphoma