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A 63-year-old man was diagnosed with a rare variant of acute promyelocytic leukemia (APL) with t(4;17)(q12; q21) that showed atypical morphological features and two different clinical symptoms. He was started on standard induction chemotherapy for acute myeloid leukemia, which decreased myeloblast numbers; however, APL-like blasts remained. He then received a salvage therapy that added all-trans retinoic acid (ATRA). After ATRA commenced, APL-like blasts disappeared and cytogenetic analysis became normal. However, myeloblasts subsequently increased, and he became resistant. In summary, this patient exhibited two different clinical courses of acute myeloid leukemia and APL.

About 5% of adult B-cell acute lymphoblastic leukemias (B-ALL) are characterized by t(4;11)(q21;q23), which confers peculiar features to this B-ALL subtype, including a very immature immunophenotype and poor prognosis. We describe the case of a 21-year-old female who presented with B-ALL carrying the t(4;11)(q21;q23) and blasts positive for CD19, TdT, CD79a, CD38, HLA-DR. Before completing the Hyper-CVAD (hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone) therapy regimen, the B-cell leukemic clone still was detected, but an additional leukemic clone appeared, with morphology and immunophenotype (CD13, CD33, CD64, CD38, CD56, CD15, CD4dim) compatible with derivation from the myeloid/monocytic lineage. Karyotype showed the co-existence of three cell lines, with persistence of t(4;11)(q21;q23) and appearance of +8,+12,+13 and two der(4). The patient died because of disseminated intravas- cular coagulation. Our report describes a rare, possible evolution of such a subtype of B-ALL, with transformation into mixed phenotype acute leukemia in the course of therapy. This finding suggests a blast cell derivation from a common lymphoid/monocytic precursor leading to a final bilineal acute leukemia.