Immunophenotyping of bone marrow trephine biopsies

Monoclonal antibodies were first developed in the late 1970s. However, it was only in the mid 1980s that the first attempts were made to apply monoclonal antibodies and immunophenotyping to bone marrow trephine (BMT) biopsies. Initially this was performed on frozen sections which gave optimal antigen preservation. Problems occurred with poor tissue morphology as the frozen sections were not decalcified and poor cytological preservation. Subsequent developments to improve the quality of BMT immunophenotyping have been: 1. Increased number of antibodies to an increased range of antigens detectable. 2. Development of methods that can be applied to decalcified paraffin embedded BMT biopsies. 3. Antigen retrieval methods (e.g. enzyme, microwave, heat) to expose tissue antigens masked by the tissue preparation (i.e. fixation and decalcification). 4. Enhanced immunostaining methods (e.g. tyramide) to amplify the signal intensity. Alkaline phosphatase or horseradish peroxidase methods are now widely applied to fixed, decalcified paraffin embedded BMT specimens. The range of antigens that can be detected is similar to that for fresh cell samples (e.g. blood). Panels of antibodies are used for BMT biopsies as there are few antibodies that are truly cell type specific. Applications of monoclonal antibodies and immunophenotyping to BMT biopsies include: 1. Assessment of bone marrow cellularity. 2. Analysis of bone marrow when there is no aspirate available (dry tap). 3. To establish the extent and pattern of disease infiltration (e.g. focal disease). 4. Disease classification (e.g. leukaemia, lymphoma). 5. To monitor residual disease following therapy. 6. Detection of metastatic disease. The developments in immunophenotyping methods over the past 10 years have resulted in processed BMT biopsies being as suitable a tissue for immuno-staining as other material. A wide range of monoclonal antibodies can now be applied to BMT biopsies and there are numerous applications to BMT biopsies.