The identical IGH-rearrangement in both neoplasms indicates transdifferentiation of the acute B-lymphoblastic leukemia into a Langerhans' cell sarcoma.
We report on a case of a 30-year-old male with acute B-lymphoblastic leukemia (B-ALL) with immunophenotype CD19(+), CD22(+), CD20(+), CD10(+), with aberrant expression of CD13 and CD117, and IgH gene rearrangements.