Introduction

Lymphoproliferative disorders frequently involve the peripheral blood and bone marrow, and bone marrow studies may be performed for primary diagnosis or as a staging procedure in patients with lymphoproliferative disorders. A primary diagnosis with accurate classification can often be made on bone marrow samples alone, if a combined morphologic and immunophenotypic approach is used. The addition of molecular or cytogenetic studies can resolve some of the low percentage of cases that are equivocal after morphologic and immunophenotypic analysis.

Many of the low-grade B-cell lymphomas will involve the bone marrow, but the precise morphologic classification of these diseases is complicated by the fact that characteristic architectural patterns seen in lymph nodes involved by these diseases are not present in the bone marrow. Despite this, many of the low-grade B-cell lymphomas have characteristic immunophenotypes that allow for proper classification. Flow cytometric immunophenotyping of involved peripheral blood or bone marrow aspirate material allows for evaluation of the largest number of antigens, as well as confirming aberrant co-expression of antigens that are characteristic of certain disease types. However, paraffin section immunophenotyping, which can be performed on core or clot biopsy material, can also be used successfully to detect many antigens of interest in these cases. The characteristic immunophenotypic features of the various small B-cell lymphoid proliferations are summarized in Table 11.1.

Molecular genetic or cytogenetic studies may also be useful in selected cases to confirm the presence of a clonal population, when the differential diagnosis is between reactive and neoplastic lymphoid proliferations (Arber, 2000).