TERMINAL DEOXYNUCLEOTIDYL TRANSFERASE STAINING IN ACUTE-LEUKEMIA AND NORMAL BONE-MARROW IN ROUTINELY PROCESSED PARAFFIN SECTIONS

Terminal deoxynucleotidyl transferase (TdT) is a nuclear protein widel y used as a marker for the diagnosis and classification of acute leuke mia. The usual methods for detecting TdT require smears, imprints, or cryostat sections of unfixed tissue. A polyclonal rabbit anti-TdT seru m was used to immunostain 54 routinely processed bone marrow sections from patients with acute leukemic disorders, using a recently describe d antigen-unmasking technique based on microwave oven heating. The spe cificity of this method of TdT analysis was confirmed by comparing the results obtained with conventional TdT analysis by indirect immunoflu orescence. Terminal deoxynucleotidyl transferase reactivity was also e valuated in 44 nonmalignant and normal bone marrow specimens. All case s that were TdT-positive by immunofluorescence (41 of 42 ''pre-B'' and T-cell acute lymphoblastic leukemia, 2 of 5 acute myeloid leukemia, a nd 1 of 5 chronic myeloid leukemia in blast crisis) were also positive in paraffin sections. The percentage fluorescence positivity correlat ed with the percentage of immunoperoxidase stained cells in 44 of 45 c ases. The remaining nonneoplastic and normal bone marrow biopsy specim ens were TdT-negative. These results show that TdT immunoperoxidase st aining of conventionally processed bone marrow specimens can be readil y achieved by the use of a simple antigen-unmasking technique and may provide useful diagnostic information particularly in cases in which f resh tissue samples are unavailable.