Background: Numerous studies have reported on the immunophenotype of plasma cells (PCs) in monoclonal gammopathy of undetermined significance (MGUS) and in plasma cell myeloma (PCM), but very few have examined the immunophenotype of normal PCs. In this study, an objective definition of normal range of expression for each antigen was found on normal control PCs. Using these new ranges of normal expression (new method) is different from using a static 20% of PCs cut-off for all antigens as described in the literature (traditional method). These newly calculated normal ranges for each antigen were applied to our data, and compared to histologic and immunohistochemical findings.Methods: Bone marrow samples from 46 patients with PC neoplasms and 15 normal controls were studied. A minimum of 100 PC were analyzed for each patient and control sample. An 8-color staining method was applied to study the immunophenotype of PCs, using a BD FACSCanto II.Results: By the new ranges of normality calculated in this study it was determined that different antigens have different level of expression on polyclonal PCs. CD19 correlated with histology by both the traditional and new methods, but had superior correlation by the new method.Conclusions: This report is the first 8-color immunophenotypic study of PCM in which a ''range of normal expression'' for each antigen is defined. This is a critical step to help distinguish between a normal and neoplastic PC immunophenotype and discern which antigens are of diagnostic importance. V C 2010
Rare cases of CD20+ T-cell lymphoma (TCL) have been reported, but the clinicopathologic spectrum of this disorder is not known. We identified 9 cases of CD20+ TCL diagnosed at our institution and 26 additional cases through a search of the English language literature. Among current cases, there were 7 men (ages 71 to 81, median 75 y) and 2 women (ages 36 and 37 y). Five patients presented with predominantly nodal disease (localized in 3 and widespread in 2 cases) and 4 patients presented with purely extranodal disease involving the parotid glands, skin, or small intestine. CD20 was uniformly and strongly expressed in 5 cases and dimly expressed or present on a subset of neoplastic cells in 4 cases. The proportion of CD20+ T cells changed over time in 3 cases. Three cases fulfilled diagnostic criteria for clinicopathologically defined subtypes of TCL (2 mycosis fungoides; 1 enteropathy-type TCL), whereas 6 were peripheral TCL unspecified with variable cytomorphology, T-cell immunophenotype, and sites of involvement. In 8 of 9 cases, a clonal T-cell population was identified by molecular genetic analysis. Among 8 cases with clinical follow-up, 5 behaved aggressively with death from disease within 3 years of diagnosis in 4 cases (median survival: 11 mo, range: 1 to 35 mo), and recurrent disease at 10 months in 1 case; 1 patient died of an EBV+ B-cell lymphoma (BCL) 66 months after the original diagnosis; in the remaining 2 cases, patients were alive and undergoing treatment (follow-up: 4 and 18 mo). Historical cases showed similar clinicopathologic variability. CD20+ TCL is rare, and clinically and pathologically heterogeneous. When CD20 expression is present in TCL, it may be dimmer than that of normal B cells, suggesting neoplastic transformation of a normal CD20dim+ T-cell subset. Cases of CD20+ TCL in which the proportion of CD20+ cells changes over time may reflect aberrant expression of CD20, possibly as an activation marker, by neoplastic T cells. CD20+ TCL may cause diagnostic difficulty, particularly in cases that clinically and pathologically mimic BCL. Knowledge of the unusual phenomenon of CD20 expression in TCL, in conjunction with careful morphologic analysis, the use of a panel of antibodies, and molecular genetic studies, is important in avoiding a misdiagnosis of BCL.
Hodgkin lymphomas are characterised by the presence of rare malignant cells in a background of non-neoplastic inflammatory cells. Flow cytometric analysis of involved tissues is generally not thought to be useful in establishing the diagnosis, because of the small number of neoplastic cells present. However, two recent studies describing a CD4+CD8+ (double-positive) T-cell population in nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) suggest that flow cytometry could play a role in the diagnosis of this Hodgkin lymphoma subtype. In addition, awareness of this unusual T-cell population is important in avoiding a misdiagnosis of a T-cell neoplasm. Although the function of CD4+CD8+ T-cells in NLPHL is not known, studies of phenotypically similar cells in other settings point to a reactive or regulatory role. CD4+CD8+ T-cells have also been identified in the benign entity progressive transformation of germinal centres (PTGC), suggesting a possible relationship between NLPHL and PTGC.
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