BILINEAL ACUTE-LEUKEMIA OF B-LINEAGE AND T-LINEAGE WITH A NOVEL TRANSLOCATION T(9-17)(P11-Q11)

We describe a case of bilineal leukemia in a 5-year old boy with a rar e immunophenotype and the novel translocation t(9;17)(p11;q11) as the sole chromosomal abnormality. Two immunologically distinct blast cell subsets expressed T-markers (CD2, CD5, CD7) and common ALL markers (Td T, CD19, CD22, CD10), respectively. Both cell populations were CD34 ne gative. The patient, who presented with CNS leukemia, responded prompt ly to standard chemotherapy for lymphoblastic leukemia and remains in complete remission 20 months from diagnosis. Other translocations betw een chromosomes 9 and 17 have been infrequently reported in a variety of leukemias but as yet their biologic significance is unknown. The cl inical course of this case suggests that t(9;17)(p11;q11) may not have an adverse influence on the disease out come. However, the role of t( 9;17) in the pathogenesis of this unusual lymphoid phenotype remains u nresolved.