Lineage switch from acute myeloid leukemia to acute lymphoblastic leukemia: report of an adult case and review of the literature.

Lineage switch from AML to ALL is an extremely rare phenomenon, and we report the case of an adult diagnosed with AML at 46 years of age who relapsed with ALL. At initial diagnosis, blast cell morphology and immunophenotyping were consistent with the diagnosis of M4-AML. Complete remission was achieved, and the patient underwent autologous BMT. At relapse, six months after ABMT, blast cells were different from those seen at initial diagnosis, for morphology (L2-ALL), cytochemistry, and immunophenotyping. The karyotype was normal at both diagnosis and relapse. No evidence of bcr-abl fusion genes was found by RT-PCR. Monoclonal IgH and TCR gamma gene rearrangement were evidenced by PCR analysis at relapse but not on blast cells at AML diagnosis.