Flow Cytometry In Neoplastic Hematology: Morphologic-Immunophenotypic Correlation, Third Edition Dow ^NEW^

The classification structure follows a lineage-based framework, flowing broadly from benign to malignant and branching down to category, family, type (disease/tumour), and subtype. Where possible, a triad of attributes was systematically applied and included: lineage + dominant clinical attribute + dominant biologic attribute. Lineage attribution rests on immunophenotyping with flow cytometry and/or immunohistochemistry. Dominant clinical attributes are general features of the untreated disease and include descriptors such as acute, chronic, cytopenia(s) (myelodysplasia) and cytosis(es) (myeloproliferation). Most biologic attributes include gene fusions, rearrangements, and mutations. Fusions are part of the nomenclature of types/subtypes when the identities of both implicated genes are required or often desirable criteria for diagnosis (e.g., PML::RARA). Rearrangements, a broad term that encompasses a range of structural genomic alterations leading to gene fusions, are part of the nomenclature of types/subtypes when there are multiple possible fusion partner genes of a biologically dominant gene (e.g., KMT2A). Of note, the use of the term rearrangements is maintained in the classification due to its wide usage across prior editions, although it is recognized that it is more appropriate for genomic modifications in genes consisting of various segments (e.g., immunoglobulin genes and T-cell receptor genes). A deliberate attempt is made to prioritize classifying tumour types based on defining genetic abnormalities where possible.

This highly illustrated, practical guide contains comprehensive coverage of all the important factors for clinical diagnosis with flow cytometry. It explains the general parameters and correlation with color histomorphological findings throughout, taking a systematic approach from basic cases to complicated problem areas. Hematopathologists and neoplastic hematologists will find this book an important resource for keeping up to date with developments in clinical practice. This second edition includes a chapter on antigen expression during myeloid and lymphoid differentiation.

Both reactive and neoplastic processes have variably unique morphologic features that if properly recognized, guide the subsequent testing. However, some reactive and neoplastic processes can present with overlapping features, and even after extensive immunophenotypic evaluation and the performance of ancillary studies, it may not be possible to conclusively determine its nature. If the lymph node architecture is altered or effaced, the predominant pattern of infiltration (eg, nodular, diffuse, interfollicular, intrasinusoidal) and the degree of alteration of the normal architecture is evaluated, usually at low magnification. When the presence of an infiltrate is recognized, its components must be characterized. If the infiltrate is composed of a homogeneous expansion of lymphoid cells that disrupts or replaces the normal lymphoid architecture, a lymphoma will be suspected or diagnosed. The pattern of distribution of the cells along with their individual morphologic characteristics (ie, size, nuclear shape, chromatin configuration, nucleoli, amount and hue of cytoplasm) are key factors for the diagnosis and classification of the lymphoma that will guide subsequent testing. The immunophenotypic analysis (by immunohistochemistry, flow cytometry or a combination of both) may confirm the reactive or neoplastic nature of the process, and its subclassification. B-cell lymphomas, in particular have variable and distinctive histologic features: as a diffuse infiltrate of large mature lymphoid cells (eg, diffuse large B-cell lymphoma), an expansion of immature lymphoid cells (lymphoblastic lymphoma), and a nodular infiltrate of small, intermediate and/or mature large B cells (eg, follicular lymphoma).

The immunophenotypic analysis will in most cases reveal whether the lymphomas is of B-, T- or NK-cell origin, and whether a lymphoma subtype associated immunophenotype is present. Typical pan B-cell antigens include PAX5, CD19, and CD79a (CD20 is less broadly expressed throughout B-cell differentiation, although it is usually evident in most mature B-cell lymphomas), and typical pan T-cell antigens include CD2, CD5, and CD7. The immature or mature nature of a lymphoma can also be confirmed by evaluation of the immunophenotype. Immature lymphomas commonly express one or more of TdT, CD10, or CD34; T-lymphoblastic lymphoma cells may also coexpress CD1a. The majority of NHLs and all HLs are derived from (or reflect) B cells at different stages of maturation. Mature B-cell lymphomas are the most common type of lymphoma and typically, but not always, express pan B-cell markers as well as surface membrane immunoglobulin, with the latter also most useful in assessing clonality via a determination of light chain restriction. Some mature B-cell lymphomas tend to acquire markers that are either never physiologically expressed by normal mature B cells (eg, cyclin D1 in mantle cell lymphoma, or BCL2 in germinal center B cells in follicular lymphoma) or only expressed in a minor fraction (eg, CD5 that is characteristically expressed in small lymphocytic and mantle cell lymphoma). The most common mature B-cell lymphomas include diffuse large B-cell lymphoma, follicular lymphoma, small lymphocytic lymphoma, mantle cell lymphoma, marginal zone lymphoma, Burkitt lymphoma, and lymphoplasmacytic lymphoma (Figures 2 and 3). Classical HLs are also lymphomas of B-cell origin that demonstrate diminished preservation of their B-cell immunophenotype (as evidenced by the dim expression of PAX5 but absence of most other pan B-cell antigens), expression of CD30, variable expression of CD15, and loss of CD45 (Figure 1). In contrast, nodular lymphocyte predominant HL shows a preserved B-cell immunophenotypic program and expression of CD45, typically without CD30 and CD15. Of note, the evaluation of the immunophenotype of the neoplastic cells in HL is routinely assessed by immunohistochemistry because most flow cytometry laboratories cannot reliably detect and characterize the low numbers of these cells. 2b1af7f3a8