Lineage switch from T-cell lymphoblastic leukemia/lymphoma to acute myeloid leukemia and back to T-cell lymphoblastic leukemia/lymphoma in a patient diagnosed during pregnancy.

Although relapse of acute leukemia is common, a change of immunophenotype at relapse only occurs rarely. Some of these cases have been labeled "lineage switch". In most cases, B-cell lymphoblastic leukemia/lymphoma (B-ALL) relapses as acute myeloid leukemia (AML). We report a rare case of T-cell acute lymphoblastic leukemia/lymphoma (T-ALL) relapsing as AML and then returning as T-ALL again in a patient who began her therapy during the third trimester of pregnancy. The patient retained the same cytogenetic and next generation molecular findings in both leukemias. This case provides further evidence of the plasticity of the leukemic stem cell.