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CHAPTER 14

Figure 14.15 Schematic representation of WHO-REAL classification of lymphoid neoplasms. Various immunophenotypes of B and T-cell
malignancies are correlated with normal immunophenotypic differentiation/maturation stages of B and T-cells in the bone marrow, lymphoid tissue,
peripheral blood and thymus. Disorders of Leucocytes and Lymphoreticular Tissues

revised European-American classification of lymphoid Leukaemias and lymphomas of T-cell origin: T-cell
neoplasms abbreviated as REAL classification. This malignancies comprise the remainder 20% cases of lymphoid
classification was based on the hypothesis that all forms of leukaemia and 10% cases of NHLs. T-cell malignancies reflect
lymphoid malignancies (NHLs as well as lymphoblastic the stages of T-cell ontogeny. Like B-cell malignancies, T-
leukaemias) represent malignant counterparts of normal cell derivatives too are further categorised into indolent and
population of immune cells (B-cells, T-cells and histiocytes) aggressive T-cell malignancies. The most widely expressed
present in the lymph node and bone marrow. It is believed T-cell antigens are CD2 and CD7.
that lymphoid malignancies arise due to arrest at the various REAL classification subsequently merged into WHO
differentiation stages of B and T-cells since tumours of histio- classification described below.
cytic origin are quite uncommon. Accordingly, it is III. WHO CLASSIFICATION OF LYMPHOID NEO-
considered essential to understand and correlate the PLASMS (1999): In view of confusion surrounding the
differentiation stages of B and T-cells with various lymphoid classification schemes of lymphoid cancer, Harris et al, who
malignancies (Fig. 14.15). REAL classification divides all described REAL classification, evolved a consensus
lymphoid malignancies into two broad groups, each having international classification of all lymphoid neoplasms together
further subtypes:
as a unified group (lymphoid leukaemias-lymphomas) under
Leukaemias and lymphomas of B-cell origin: B-cell derivation the aegis of the WHO. Although this classification has many
comprises 80% cases of lymphoid leukaemias and 90% cases similarities with REAL classification as regards identification
of NHLs. Based upon these phenotypic and genotypic of B and T cell types (Fig. 14.15), WHO classification has more
features, B-cell neoplasms are of pre-B and mature B-cell classes. WHO classification takes into account morphology,
origin. Based on their biologic behaviour, B-cell malignancies clinical features, immunophenotyping, and cytogenetic of the
are further subclassified into indolent and aggressive. All tumour cells. Hence, on this basis, it is possible to know the
these tumours express Pan-B (CD19) antigen besides other stage of maturity of the neoplastic cell and thus has a better
markers. clinical and therapeutic relevance.