We describe a 40-year-old woman with a history of precursor T-cell acute lymphoblastic leukemia who developed an orbital mass associated with diffuse infiltration of the paranasal sinuses. The clinical and radiologic findings suggested an orbital abscess. Examination of orbital and ethmoid sinus biopsy specimens revealed relapse of precursor T-cell acute lymphoblastic leukemia. Although orbital...

An increasing number of reports document instances in which individual leukemic cells coexpress markers normally believed to be restricted to a single lineage. This has been interpreted by McCulloch and colleagues as aberrant programming or lineage infidelity and contrasts with earlier suggestions that lineage fidelity of gene expression was usually maintained in leukemia. We argue that several...

A recent report by Pui et all focused on the biologic and clinical relevance of acute mixed-lineage leukemia; namely, acute lymphoblastic leukemia expressing myeloid-associated antigens (My+ ALL) and acute myeloid antigens expressing lymphoid antigens (Ly+ AML) were analyzed in a pediatric series. In our opinion, a major point in the field of hybrid acute leukemia remaining undetermined is whic...

Fusion proteins composed of the histone methyltransferase mixed-lineage leukemia (MLL) and a variety of unrelated fusion partners are highly leukemogenic. Despite their prevalence, particularly in pediatric acute leukemia, many molecular details of their transforming mechanism are unknown. Here, we provide mechanistic insight into the function of MLL fusions, demonstrating that they capture a t...

Mixed-lineage leukemia (MLL) fusion proteins are potent inducers of leukemia, but how these proteins generate aberrant gene expression programs is poorly understood. Here we show that the MLL-AF4 fusion protein occupies developmental regulatory genes important for hematopoietic stem cell identity and self-renewal in human leukemia cells. These MLL-AF4-bound regions have grossly altered chromati...

Myeloid sarcoma, which sometimes accompanies recurrent systemic leukemia, is a rare manifestation of congenital leukemia. We describe the case of a 1-month-old Japanese girl with myeloid sarcoma, who did not fulfill the criteria of systemic leukemia. The physical examination revealed a bruise-like plaque on the right side of her chest. Histopathologically, there were CD4+ CD56- CD68+ atypical l...

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder where over a period of time 15-20% of patients show blastic transformation with majority transforming into acute myeloid leukemia, most of which are of granulocytic lineage. Erythroid blast phase of CML is relatively rare with the incidence ranging from 0-10%. Further the incidence of acute erythroid leukemia by itself is fairl...

Cellular accumulation of methotrexate polyglutamates (MTXPGs) is recognized as an important determinant of the cytotoxicity and selectivity of methotrexate in acute lymphoblastic leukemia (ALL). We identified a significantly lower cellular accumulation of MTXPGs in T-lineage versus B-lineage lymphoblasts in children with ALL, which is consistent with the worse prognosis of T-lineage ALL when tr...

Six cases of acute leukemia that underwent lineage switch from acute lymphocytic leukemia to acute myelogenous leukemia are reported. The mean age of the patients was 24 years, time to conversion was 36 months, and survival after conversion was only 3 months. Of the three cases which showed abnormal metaphases at both diagnosis and conversion, two (cases 2, 5) showed related cytogenetic abnorma...

Mixed lineage leukemia is a very aggressive blood cancer that predominantly occurs in pediatric patients. In contrast to other types of childhood acute leukemias, mixed lineage leukemia presents with a dismal prognosis and despite the availability of advanced treatment methods cure rates have stagnated over the last years. Mixed lineage leukemia is characterized by the presence of MLL fusion pr...