Paraffin section immunophenotyping of acute leukemias in bone marrow specimens

The immunohistochemical evaluation of acute leukemia specimens has been limited in the past due of the inability to detect many lineage-related antigens in paraffin sections. With the improvement in immunohistochemical methods as well as the introduction of new antibodies, these limitations are now reduced. To evaluate the diagnostic utility of paraffin section immunohistochemistry in the lineage determination of acute leukemias, 77 previously immunophenotyped acute leukemias were studied with a panel of antibodies that included antibodies directed against CD3, CD20, CD34, CD43, CD68, CD79a, HLA-DR, myeloperoxidase (MPX), and terminal deoxynucleotidyl transferase (TdT). The cases included 48 acute myeloid leukemias, 18 precursor B-cell acute lymphoblastic leukemias, 6 T-cell acute lymphoblastic leukemias, and 5 mixed precursor B/myeloid leukemias. This immunohistochemical panel correctly identified the lineage of 96% of both acute myeloid leukemias and acute lymphoblastic leukemias and identified evidence of mixed lineage in 60% of mixed lineage leukemias. Antibodies directed against CD3, CD79a, MPX, and TdT were found to be the most useful, although the latter three alone were not entirely lineage specific. These findings suggest a role for paraffin section immunohistochemistry in the lineage determination of some cases of acute leukemia.