Cytoplasmic CD3 expression in infant acute megakaryoblastic leukemia: A new ambiguous lineage subtype?

Several conventions have been established in order to define and characterize Mixed Phenotype Acute Leukemia (MPAL). However, megakaryocytic markers have not been included in the definition of MPAL neither in the European Group for the Immunological Characterization of Leukemias (EGIL) proposal nor in any of the WHO Classification of Tumors issues. We report four pediatric acute leukemia (AL) cases (prevalence: 0.18%) with megakaryoblasts co-expressing the T-specific antigen CD3 (cytoplasmic), together with a very homogeneous antigen profile of immature cells and other lymphoid traits. In one case, the presence of epsilon CD3 mRNA was confirmed as well on sorted CD34+ blasts. All four cases were infants, and two of them disclosed trisomy 21 in the blast population (not constitutional) without being children with Down Syndrome. They were homogeneously treated with AML schemes, achieving all four CR. However, 3 patients relapsed early. Only one patient is alive and remain disease-free, with a long follow-up. Even though cyCD3 was the only T cell marker expressed, its specificity entails the consideration of these cases as a new subtype of MPAL Megakaryoblastic/T, keeping this in mind when designing diagnostic panels. Detection and report of these cases are necessary so as to further characterize them in order to define the most appropriate treatment.

A case of acute megakaryoblastic leukaemia (FAB M7), a rare type of acute myeloid leukemia (AML), in a teenager.

Acute Megakaryoblastic Leukaemia (AML, M7) is a rare type of acute myeloid leukemia (AML) evolving from primitive megakaryoblasts. It accounted for 1.2% of newly diagnosed AML according to Eastern Cooperative Oncology Group (ECOG) trials between 1984 and 1997. Patients may present with a broad variety of symptoms including low-grade fever, easy bruising, and life-threatening conditions. We report a rare case of AML, M7 in a 19-year-old lady who presented with weakness and fatigue. She was diagnosed as a case of AML, M7 on the basis of peripheral blood finding, bone marrow examination report, radiological findings and immunophenotyping.

Pan myeloid antigen-negative pediatric acute megakaryoblastic leukemia.

Acute megakaryoblastic leukemia (AMKL) is a relatively common type of acute myeloid leukemia in children. We describe two unusual cases of AMKL that by flow cytometry (FC) lacked expression of any commonly evaluated myeloid antigens. One case presented as a periorbital myeloid sarcoma and clinically was thought to be a solid tumor. In both cases, the leukemic blasts were variably positive for the megakaryocytic marker CD61. Cytogenetics confirmed the presence of the t(1;22) in one case. Cytogenetics and inclusion of megakaryocytic markers in FC panels when evaluating pediatric specimens is critical for appropriate diagnosis for myeloid antigen negative AMKL.

Spontaneous remission of childhood acute marrow fibrosis and megakaryoblastic leukemia.

Spontaneous remission in 2 children with myelofibrosis, one with megakaryocytic acute myeloblastic leukemia and t(1;22) (with recurrence later) and one with Down syndrome and GATA1 mutation (permanent), are described. One had sepsis and was treated with antibiotics and blood products, whereas the other received only blood products. Remission was spontaneous, without chemotherapy treatment. Possible explanations for these outcomes include immunologic response to sepsis by a leukemia-specific T-cell response or the release of various cytokines, such as tumor necrosis factor and interleukin-2, during infections. Natural killer and cytotoxic T cells transfused with blood products might have also triggered an immune response.

Acute megakaryoblastic leukaemia (AMKL) in children: a comparison of AMKL with and without Down syndrome.

To characterize childhood acute megakaryoblastic leukaemia (AMKL), we reviewed 45 children with AMKL diagnosed between 1986 and 2005 at Nagoya University Hospital and Japanese Red Cross Nagoya First Hospital. Twenty-four patients (53%) had AMKL associated with Down syndrome (DS-AMKL) and 21 (47%) had non-DS-AMKL. The median age of the DS-AMKL patients was 21 months (range, 8-38 months) and that of non-DS-AMKL patients was 15 months (range, 2-185 months). The morphology of blast cells was categorized into three groups according to the stage of megakaryocyte maturation. The blast cells were more immature in DS-AMKL than in non-DS-AMKL in terms of morphology and immunophenotyping. Cytogenetic abnormalities of leukaemic cells were classified into seven categories: normal karyotype including constitutional trisomy 21 in DS-AMKL; numerical abnormalities only; t(1;22)(p13;q13); 3q21q26 abnormalities; t(16;21)(p11;q22); -5/del(5q) and/or -7/del(7q); and other structural changes. The outcome of children with either DS-AMKL or non-DS-AMKL is excellent. The 10-year overall survival estimate was 79% [95% confidence interval (CI): 54-90] for DS-AMKL and 76% (95% CI: 58-91) for non-DS-AMKL (P = 0.81) with a median follow-up of 78 months (range, 20-243 months). Our study shows the diverse heterogeneity of childhood AMKL and the need for subclassification according to cytogenetic and morphological features.

CD34+, CD41+ acute megakaryoblastic leukemia in a dog.

A clinically normal, 5-year-old intact female German Shepherd dog was presented to the local veterinarian to be spayed. Results of a preoperative CBC included mild nonregenerative anemia, severe thrombocytopenia, and 17% unclassified cells. On cytologic examination of aspirates from the dog's enlarged spleen and peripheral lymph nodes, a population of primitive round cells that occasionally resembled megakaryocytes was observed. A bone marrow aspirate specimen was markedly hypercellular with approximately 65% of marrow cells comprising a homogeneous population of immature hematopoietic cells similar to those found in the spleen, lymph nodes, and peripheral blood. Using immunocytochemical stains with canine-specific antibodies, all neoplastic cells strongly expressed cytoplasmic CD41 and 20-70% of the neoplastic cells expressed CD34 weakly to moderately. Rare (<0.5%) neoplastic cells weakly expressed vWF. The cells were negative for all other markers. Based on these results and the morphology of the neoplastic cells, a diagnosis of acute megakaryoblastic leukemia (AMegL) was made. In spite of treatment, results of a CBC performed 1 week later indicated progressive anemia and thrombocytopenia, and the dog was euthanized. To our knowledge, this report documents the first case of canine AMegL diagnosed with both anti-canine CD34 and CD41 antibodies.

[Childhood acute megakaryoblastic leukemia].

The aim of this study was to investigate the clinical, pathological and biological features of acute megakaryoblastic leukemia in childhood. The morphology of cells was observed by means of bone marrow smear; the immunophenotype was detected by flow cytometry and immunohistochemistry assay. The results indicated that the fever, hemorrhage, hepatosplenomegaly and lymphadenopathy in this case were the primary presentations accompanying by leukocytosis, anemia and thrombocytopenia. An adequate marrow aspirate could not be obtained. At the time of diagnosis, the bone marrow had more than 30% megakaryoblasts in nucleated cells. Flow cytometric analysis revealed the dual expression of CD41 and CD61 by tumor cells in bone marrow. The histopathological examination of bone marrow demonstrated infiltration of large-sized CD42b(+) cells. According to all above mentioned results, this case was diagnosed as acute megakaryoblastic leukemia. In conclusion, childhood acute megakaryoblastic leukemia is a rare and easily misdiagnosed disease with poor prognosis. Flow cytometry analysis and immunohistochemistry assay of bone marrow can help in detecting this leukemia subtype and evaluating its prognosis.

Acute myeloid leukaemia of mixed megakaryocytic and erythroid origin: a case report and review of the literature.

We report the case of a 78-year-old man who presented with acute myeloid leukaemia showing subpopulations of cells expressing platelet-associated markers and the presence of a pan-myeloid component, besides glycophorin A-positive cells. Most of the immature cells had a proerythroblast-like morphology and we classified this case as an FAB-M6 variant, as suggested by Bain (1). According to the WHO classification, this leukaemia fulfilled the criteria of'AML with multilineage dysplasia' (2). Immunophenotyping characteristics showed two distinct aberrant subpopulations, a young pan-myeloid (CD45+ with low density, CD34+, CD117+, CD13+, CD33+, partial cytoplasmic myeloperoxidase (MPO)+) population with platelet-associated markers (CD41+, CD42+, CD61+) and a CD45+, CD117+, CD34- population with partial CD235a positivity indicative for erythroid maturation. This case belongs to the group of 'early' erythroblastic leukaemias where a subset of progenitor cells present with erythroid-megakaryocyte bipotentiality or are blocked at an early BFU-E (burst-forming unit erythrocyte)-like stage of erythroid differentiation (11, 12, 13).

Standard induction chemotherapy followed by attenuated consolidation in elderly patients with acute myeloid leukemia.

The benefits of intensive post-remission chemotherapy have not been verified in elderly patients with acute myeloid leukemia (AML). To reduce fatal complications caused by intensive post-remission therapy, we performed a prospective phase II multicenter trial of standard induction chemotherapy ('7+3' of cytarabine plus daunorubicin), followed by two cycles of attenuated consolidation therapy ('5+1' of cytarabine plus daunorubicin) for elderly patients with AML, excluding those with M3. Of the 41 patients enrolled in the study, 24 (58.5%) attained CR. Of these 24, 17 (70.8%) completed both planned cycles of consolidation therapy. After a median follow-up of 566 days (range, 63-1190 days) among surviving patients, 15 relapsed, with an actuarial 3-year disease-free survival rate of 22.5%. There were no fatal complications during consolidation therapy. Actuarial 3-year overall survival was 17.0%. These findings suggest that, when compared with previous findings using more intensive consolidation therapy, attenuated consolidation therapy does not compromise outcomes in elderly AML patients.

Novel insights into the pathogenesis of the Graffi murine leukemia retrovirus.

The Graffi murine leukemia virus (MuLV) was isolated in 1954 by Arnold Graffi, who characterized it as a myeloid leukemia-inducing retrovirus. He and his team, however, soon observed the intriguing phenomenon of hematological diversification, which corresponded to a decrease of myeloid leukemias and an increase of other types of leukemias. Recently, we derived two different molecular clones corresponding to ecotropic nondefective genomes that were named GV-1.2 and GV-1.4. The induced leukemias were classified as myeloid based on morphological analysis of blood smears. In this study, we further characterized the two variants of the Graffi murine retrovirus, GV-1.2 and GV-1.4, in three different strains of mice. We show that the Graffi MuLV is a multipotent retrovirus capable of inducing both lymphoid (T- and B-cell) and nonlymphoid (myeloid, erythroid, megakaryocytic) leukemia. Many of these are very complex with concomitant expression of different hematopoietic lineages. Interestingly, a high percentage of megakaryocytic leukemias, a type of leukemia rarely observed with MuLVs, arise in the FVB/n strain of mice. The genetic backgrounds of the different strains of mice influence greatly the results. Furthermore, the enhancer region, different for GV-1.2 and GV-1.4, plays a pivotal role in the disease specificity: GV-1.2 induces more lymphoid leukemias, and GV-1.4 induces more nonlymphoid ones.

Immunophenotype of Down syndrome acute myeloid leukemia and transient myeloproliferative disease differs significantly from other diseases with morphologically identical or similar blasts.

BACKGROUND AND OBJECTIVES: Children with Down Syndrome (DS) have a 20-40 fold increased risk of developing acute myeloid leukemia (AML), mainly of the megakaryoblastic subtype (AMKL). Approximately 10 % of newborns with DS show transient myeloproliferative disease (TMD) which normally resolves spontaneously. The blast cells of both entities show megakaryoblastic/erythroblastic features (M7/M6) and cannot be distinguished by morphological characteristics. DESIGN AND METHODS: Blast cells of 62 children were analyzed by four-color flow cytometry and dual color fluorescence microscopy. RESULTS: The immunophenotype of blast cells from children with TMD and DS-AMKL is characterized by the expression of CD33 (+)/CD13 (+/-)/CD38 (+)/CD117 (+)/CD34 (+/-)/CD7 (+)/CD56 (+/-)/CD36 (+)/CD71 (+)/CD42b (+)/CD4dim (+)/TPO-R (+)/EPO-R (-)/IL-3-Ralpha (+)/IL-6-Ralpha (-). Non-DS children with morphologically related diseases, i. e. myelodysplastic syndrome (MDS), juvenile myelomonocytic leukemia (JMML), or AML-M6 and AML-M7, did not show this expression profile. CD34 expression was observed in 93 % of TMD, but only 50 % of DS-AMKL patients. The blast cells of all TMD and DS-AMKL cases were positive for TPO-R and IL-3R, whereas EPO-R and IL-6R were absent. CONCLUSIONS: Immunophenotyping by the use of surface antigens and growth factor receptors is a useful tool to discriminate TMD and DS-AMKL from diseases with morphologically similar or identical blasts. The absence of EPO-R on the blast cells might be a sign of the high expression of the mutated -- and less active -- GATA1 in DS. The higher amount of CD34 co-expression in TMD may be interpreted to indicate that TMD is a slightly more immature disease than DS-AMKL.

Hematopoietic stem cell transplantation for de novo acute megakaryocytic leukemia in first complete remission: a retrospective study of the European Group for Blood and Marrow Transplantation (EBMT).

Acute megakaryoblastic leukemia (M7 AML) is a highly aggressive disease. We evaluated outcomes in 57 children (11 with Down syndrome) and 69 adults with M7 AML after first complete remission (CR1) following autologous or HLA-identical allogeneic transplantation. Characteristics of the recipients of autologous transplants (38 children, 37 adults) were, respectively: median age, 1.7 and 46 years; non-total body irradiation (non-TBI) conditioning regimen, 97% and 70%; bone marrow as stem cell source, 74% and 43%. Characteristics of the recipients of allogeneic transplants (19 children, 32 adults) were, respectively: median age, 2.8 and 37 years; non-TBI regimen, 63% and 42%; bone marrow as stem cell source, 95% and 69%. Autologous transplantation benefited children more; the relapse rate was high in adults. Results for autologous transplantation were (children and adults, respectively): engraftment, 90% and 100%; 3-year treatment-related mortality (TRM) rate, 3% and 8%; relapse rate, 45% and 64%; leukemia-free survival (LFS) rate, 52% and 27%; overall survival (OS) rate, 61% and 30%. After allogeneic transplantation, TRM was fairly low in children and adults, and relapse rates were lower than after autologous transplantation. Results for allogeneic transplantation were, respectively: engraftment, 95% and 90%; TRM, 0% and 26%; relapse rate, 34% and 28%; LFS, 66% and 46%; OS, 82% and 43%). We conclude that M7 AML patients in CR1 (except children with Down syndrome, who already have better outcomes) can benefit from transplantation.

Acute panmyelosis with myelofibrosis: an entity distinct from acute megakaryoblastic leukemia.

The WHO criteria for diagnosing acute panmyelosis with myelofibrosis are somewhat distinct from those for acute megakaryoblastic leukemia. However, clinical and hematopathologic findings partially overlap. This has raised questions as to whether these are indeed separate, definable entities. To determine the potential importance of bone marrow biopsy supplemented by immunohistochemistry in distinguishing between these two conditions, we studied 17 bone marrow biopsies of well-characterized cases of acute panmyelosis with myelofibrosis (six cases) and acute megakaryoblastic leukemia (11 cases). We compared blast frequency, reticulin content, CD34 expression, and the degree of megakaryocytic differentiation of the blast cells in these two conditions. Our results demonstrate important differences. Acute panmyelosis with myelofibrosis is characterized by a multilineage myeloid proliferation with a less numerous population of blasts than acute megakaryoblastic leukemia (P<0.01). In the former condition, blasts are always positive with CD34, while in acute megakaryoblastic leukemia they express CD34 in 60% of the cases. The blasts in acute panmyelosis with myelofibrosis only rarely express megakaryocytic antigens. By contrast, acute megakaryoblastic leukemia has a significantly higher proportion of blasts expressing megakaryocytic antigens (P<0.01 with CD42b). Our results confirm that histology supplemented by immunohistochemistry permits the distinction of these conditions in routinely processed bone marrow biopsies.

Cytogenetic profile of childhood and adult megakaryoblastic leukemia (M7): a study of the Groupe Français de Cytogénétique Hématologique (GFCH).

To draw the cytogenetic profile of childhood and adult acute megakaryoblastic leukemia (M7), the Groupe Français de Cytogénétique Hématologique collected 53 cases of M7 (30 children and 23 adults). Compared to other acute myeloid leukemias, M7 is characterized by a higher incidence of abnormalities, a higher complexity of karyotypes, and a different distribution of abnormalities among children and adults. Nine cytogenetic groups were identified: normal karyotypes (group 1), patients with Down syndrome (group 2), numerical abnormalities only (group 3), t(1;22)(p13;q13) or OTT-MAL transcript (group 4), t(9;22)(q34;q11) (group 5), 3q21q26 (group 6), -5/del(5q) or -7/del(7q) or both (group 7), i(12)(p10) (group 8), and other structural changes (group 9). Groups 1, 2, 3, and 4 were exclusively composed of children (except one adult in group 3), whereas groups 5, 6, 7, and 8 were mainly made up of adults. The main clinical and hematologic features of these groups were described. No new recurrent abnormality was identified, but mapping of all breakpoints allowed us to specify several possible hot spots of rearrangement: 17q22-23, 11q14-21, 21q21-22, and 16q21-22-23. Although 90.5% of cases had no documented antecedent hematologic disorder or exposure to chemotherapy or radiotherapy, the morphologic and the cytogenetic findings indicated that M7 might be a secondary leukemia more often than suggested by preceding history, particularly among adults. The concurrent analyses of morphologic and cytogenetic data also led us to assume that the initial precursor involved might be more immature in adult than in childhood M7.

Mutations of the AML1 gene in acute myeloid leukemia of FAB types M0 and M7.

The AML1 gene encodes a transcription factor that, together with its heterodimeric partner CBFB, regulates a number of target genes that are essential for normal hemopoiesis. In acute myeloid leukemia (AML), AML1 is disrupted not only by chromosomal translocations but also by mutations in the runt domain, which binds both DNA and CBFB. Acquired mutations have been described predominantly in the AML FAB type M0. To date, most patients appear to have biallelic disease, suggesting a complete lack of normal AML1 function. Inherited loss of function mutations thought to lead to haploinsufficiency also have been described in patients who have a familial disorder with predisposition to AML (FPD/AML), indicating the role of AML1 in megakaryopoiesis. Using single-strand conformation polymorphism analysis, we studied the AML1 runt domain in 41 patients with M0 AML and identified potentially pathologic mutations in five (12%). Biallelic disease could be confirmed in only one patient, using loss of heterozygosity studies. At least three of the mutations would lead to truncated proteins similar to those reported in FPD/AML, suggesting that haploinsufficiency plays a role in the pathogenesis of this minimally differentiated type of leukemia. The incidence of acquired mutations in AML patients with acute megakaryoblastic leukemia (FAB type M7) was the same as that reported in other non-M0 patients, with only one mutation detected in 20 (5%) patients studied.