T-Cell Receptor and Immunoglobulin Gene Rearrangements in Acute Myeloid and Undifferentiated Leukemias of Adults: Correlation with Weak Surface Expression of CD45 and CDw52 Antigens

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Abstract
We examined 150 cases of acute myeloid leukemia (AML) and 8 cases of acute undifferentiated leukemi (AUL) of adults for both phenotypic and genotypic evidence of commitment to the lymphoid lineages. There was no correlation between expression of lymphoid differentiation antigens and rearrangement of T-cell receptor (TCR) and immunoglobulin (Ig) DNA sequences. In particular 8 cases of CD7(+) AML were germline for all TCR α, β,μ, and δ Also none of the 11 cases with IgJH rearrangement expressed CD19 either on the cell surface or within the cytoplasm. Ten out of 13 cases with TCR/Ig gene rearrangement were either cytologically undifferentiated AML of FAB type M1 or AUL. None had clear immunophenotypic evidence for commitment to lymphoid lineages but 9 expressed only very small amounts of CD45 'framework' antigens and 7 expressed small amounts of CDw52 (CAMPATH-1). This phenotypic combination is otherwise seen only in precursor B cell ALL. TCR/Ig gene rearrangement in AML and AUL of adults appears to have become dissociated from the rest of the lymphoid differentiation 'program'. Recognition of these cases may be facilitated by the weak expression of both CD45 and CDw52 antigens.