Refined diagnostic criteria and classification of mast cell leukemia (MCL) and myelomastocytic leukemia (MML): a consensus proposal

Mast cell leukemia (MCL), the leukemic manifestation of systemic mastocytosis (SM), is characterized by leukemic expansion of immature mast cells (MCs) in the bone marrow (BM) and other internal organs; and a poor prognosis. In a subset of patients, circulating MCs are detectable. A major differential diagnosis to MCL is myelomastocytic leukemia (MML). Although criteria for both MCL and MML have been published, several questions remain concerning terminologies and subvariants. To discuss open issues, the EU/US-consensus group and the European Competence Network on Mastocytosis (ECNM) launched a series of meetings and workshops in 2011-2013. Resulting discussions and outcomes are provided in this article. The group recommends that MML be recognized as a distinct condition defined by mastocytic differentiation in advanced myeloid neoplasms without evidence of SM. The group also proposes that MCL be divided into acute MCL and chronic MCL, based on the presence or absence of C-Findings. In addition, a primary (de novo) form of MCL should be separated from secondary MCL that typically develops in the presence of a known antecedent MC neoplasm, usually aggressive SM (ASM) or MC sarcoma. For MCL, an imminent prephase is also proposed. This prephase represents ASM with rapid progression and 5%-19% MCs in BM smears, which is generally accepted to be of prognostic significance. We recommend that this condition be termed ASM in transformation to MCL (ASM-t). The refined classification of MCL fits within and extends the current WHO classification; and should improve prognostication and patient selection in practice as well as in clinical trials.

Genome-wide analysis of acute myeloid leukemia with normal karyotype reveals a unique pattern of homeobox gene expression distinct from those with translocation-mediated fusion events

Gene expression profiles were determined from presentation peripheral blood and bone marrow samples of 28 patients with acute myeloid leukemia (AML). Hierarchical clustering sorted the profiles into separate groups, each representing one of the major cytogenetic classes in AML [i.e., t(8;21), t(15;17), inv(16), 11q23, and normal karyotype]. Statistical group comparison identified genes whose expression was strongly correlated with these chromosomal classes. Moreover, the normal karyotype AMLs were characterized by distinctive up-regulation of certain members of the class I homeobox A and B gene families, implying a common underlying genetic lesion. These data reveal novel diagnostic and therapeutic targets and demonstrate the potential of microarray-based dissection of AML.

Cell markers in the recognition of acute myeloblastic leukaemia subtypes

The diagnosis of acute myeloblastic leukaemia (AML) is based on cell morphology, cytogenetic and molecular changes, cell markers and clinical data. Our aim was to establish whether morphology and cell markers are comparable in the evaluation of AML. Bone marrow smears were analysed, and flow cytometry and monoclonal antibodies were used to determine cell type and maturity. Morphology and cell markers correlated differently in different AML subtypes.

Detection of inv(16) and t(16;16) by fluorescence in situ hybridization in acute myeloid leukemia M4Eo

BACKGROUND AND OBJECTIVE

It has been established that cytogenetic findings at the time of diagnosis of acute myeloid leukemia (AML) are powerful prognostic indicators. Pericentric inversion of chromosome 16 and translocation t(16;16) resulting in chimeric fusion of CBFB and MYH11 genes are typically seen in the M4-Eo FAB classification subset of AML and are associated with low-risk disease. These subtle chromosomal abnormalities may be difficult to detect in poor-quality metaphase preparations and if missed could lead to incorrect assignment to risk groups and influence the therapy decision-making process.

DESIGN AND METHODS

We prospectively studied, at diagnosis, 10 patients with AML-M4 Eo by cytogenetics and fluorescent in situ hybridization (FISH) with two cosmids (36 and 40). As a control group, 7 patients (5 with a diagnosis of AML other than M4 Eo and two cases of reactive eosinophilia) were analyzed. In addition reverse transcriptase chain reaction (RT-PCR) studies were carried out in 6 cases.

RESULTS

Karyotypic analysis detected the inv(16) in all but one of the patients with M4-Eo while none of the control cases showed any abnormality on chromosome 16. FISH studies showed that all 10 patients had abnormalities on chromosome 16; the patient with normal karyotype showed an inv(16) by FISH, while a case with inv(16) by cytogenetics had a t(16;16) by FISH. RT-PCR demonstrated amplification of the CBFB/MYH11 product in all cases analyzed.

INTERPRETATION AND CONCLUSIONS

In patients with M4Eo and rearrangements of chromosome 16, FISH studies may afford more complete information than conventional cytogenetics and can be an alternative to RT-PCR studies.

Introduction of a cis-acting mutation in the capsid-coding gene of moloney murine leukemia virus extends its leukemogenic properties

Inoculation of newborn mice with the retrovirus Moloney murine leukemia virus (MuLV) results in the exclusive development of T lymphomas with gross thymic enlargement. The T-cell leukemogenic property of Moloney MuLV has been mapped to the U3 enhancer region of the viral promoter. However, we now describe a mutant Moloney MuLV which can induce the rapid development of a uniquely broad panel of leukemic cell types. This mutant Moloney MuLV with synonymous differences (MSD1) was obtained by introduction of nucleotide substitutions at positions 1598, 1599, and 1601 in the capsid gene which maintained the wild-type (WT) coding potential. Leukemias were observed in all MSD1-inoculated animals after a latency period that was shorter than or similar to that of WT Moloney MuLV. Importantly, though, only 56% of MSD1-induced leukemias demonstrated the characteristic thymoma phenotype observed in all WT Moloney MuLV leukemias. The remainder of MSD1-inoculated animals presented either with bona fide clonal erythroid or myelomonocytic leukemias or, alternatively, with other severe erythroid and unidentified disorders. Amplification and sequencing of U3 and capsid-coding regions showed that the inoculated parental MSD1 sequences were conserved in the leukemic spleens. This is the first report of a replication-competent MuLV lacking oncogenes which can rapidly lead to the development of such a broad range of leukemic cell types. Moreover, the ability of MSD1 to transform erythroid and myelomonocytic lineages is not due to changes in the U3 viral enhancer region but rather is the result of a cis-acting effect of the capsid-coding gag sequence.

Classification of acute myeloid leukaemia in trephine biopsies with special reference to lactoferrin

In spite of advances in immunohistochemical techniques, the histological subclassification of acute myeloid leukaemia (AML) in bone marrow biopsy has remained difficult. In particular, the translation of the diagnostic criteria of the French-American-British (FAB) cooperative group as primarily defined by bone marrow cytology into histology poses considerable problems. In this study, we investigated the expression of lactoferrin (LF) in various subtypes of AML and studied the usefulness of its immunohistochemical detection combined with a panel of antibodies directed against myeloperoxidase (MPOX), lysozyme (LYS), CD34 and naphthol-AS-D-chloroacetate esterase (NACE) staining in solving this problem. Trephine biopsies of 52 cases of AML were selected for histological evaluation in comparison to bone marrow aspirates classified according to FAB (M1 n = 10, M2 n = 7, M3 n = 11, M4 n = 13 and M5 n = 11). The results obtained confirmed the specificity of LF as a marker for secondary granules in neutrophilic myeloid cells and as a tool to subclassify AML. Its parallel application with (immuno-)staining for MPOX, LYS and NACE has allowed the identification of M1, M3, M5 cases, where there LF is lacking. Typically M2 is characterized by a subpopulation of LF-positive cells which tend to display a myelocytic differentiation. However, M4 shows a heterogeneous expression pattern of LF: M4a may be defined as more immature variant without LF expression while in M4b a more mature myeloid subpopulation stains positive for LF.

Detection of CBFbeta/MYH11 fusion transcripts in acute myeloid leukemia: heterogeneity of cytological and molecular characteristics

Pericentric inversion of chromosome 16, translocation (16;16) and del(16q), resulting in a chimerical fusion of CBFbeta and MYH11 genes, are typically seen in the M4Eo French-American-British (FAB) classification subset of acute myelogenous leukemia (AML). In this study, we analyzed 70 cases of acute non-lymphoblastic leukemia, mainly of the M4 or M5 type. We report the very unusual presence of the t(16;16) and CBFbeta/MYH11 fusion transcript in an M7 patient. Ten M4Eo and four non-M4Eo patients presented an inv(16), t(16;16) or CBFbeta/MYH11 fusion transcript. In most cases, the common 'A-type' CBFbeta/MYH11 fusion transcript was detected. In addition to the eight different breakpoints and the three alternative splicing variants already described, evidence of a new CBFbeta/MYH11 fusion transcript was found which involves a 785-bp deletion of MYH11. Moreover, two patients had an unusual transcript, to our knowledge only observed once. Only one patient had abnormal eosinophilic differentiation without chromosome 16 cytogenetic abnormalities or detectable CBFbeta/MYH11 fusion. Conversely, only one patient presented CBFbeta/MYH11 fusion without abnormal eosinophilic differentiation. Altogether, our data suggest a correlation between the CBFbeta/MYH11 fusion transcript and characteristic abnormal eosinophilic differentiation, whatever the FAB subtype or the percentage of abnormal eosinophils

Morphological subtyping of acute myeloid leukemia with maturation (AML-M2): homogeneous pink-colored cytoplasm of mature neutrophils is most characteristic of AML-M2 with t(8;21)

Morphologic and cytochemical features of 30 acute myeloid leukemia subtype M2 (AML-M2) patients with t(8;21) were compared with those of 50 AML-M2 patients without t(8;21). It was disclosed that irregular nuclear shape, Auer bodies, and at least 90% myeloperoxidase positivity in blast cells, and pseudo-Pelger-Huët anomaly of the nuclei and homogeneous pink-colored cytoplasm of mature neutrophils were observed in 90-100% of the t(8;21)+ patients. The percentages of patients showing these features were significantly (P < 0.01) lower in the t(8;21)- group. Among these morphological features, homogeneous pink-colored cytoplasm of mature neutrophils is most characteristic of t(8;21)+ AML-M2, because it was seen in 90% of the t(8;21)+ patients but in only 2% of the t(8;21)- patients. Conversely, pale-colored cytoplasm without any granules in mature neutrophils or dyserythropoietic features was observed in 84% of the t(8;21)- patients, but in none of the t(8;21)+ patients. These data suggest that it is possible to subtype AML-M2 patients morphologically by the recognition of homogeneous pink-colored or pale-colored cytoplasm of mature neutrophils and dyserythropoietic features. Thus, the morphologic subtyping of AML-M2 can be utilized alone or in combination with chromosomal or molecular subtyping for biological and clinical studies of AML with maturation.

The abnormal eosinophils are part of the leukemic cell population in acute myelomonocytic leukemia with abnormal eosinophils (AML M4Eo) and carry the pericentric inversion 16: a combination of May-Grünwald-Giemsa staining and fluorescence in situ hybridization

The French-American-British subtype acute myelomonocytic leukemia with abnormal eosinophils (FAB AML M4Eo) with pericentric inversion of chromosome 16 is cytomorphologically defined by a myelomonoblastic blast population and abnormal eosinophils. Until now, it remained an open question whether these abnormal eosinophils are part of the malignant clone or an epiphenomenon. We analyzed five cases of AML M4Eo with inv(16) and combined May-Grünwald-Giemsa staining with fluorescence in situ hybridization using yeast artificial chromosome clone 854E2, which spans the inv(16) breakpoint on 16p. In the case of inv(16), three instead of the normal two hybridization signals can be observed both on metaphase spreads and in interphase cells. With this approach, we were able to show inversion 16 in abnormal eosinophils and, therefore, identified them as a part of the leukemic cell population.

A distinct subtype of M4/M5 acute myeloblastic leukemia (AML) associated with t(8:16)(p11:p13), in a patient with the variant t(8:19)(p11:q13)--case report and review of the literature

Acute myeloblastic leukemia (AML) with t(8:16) or its variant t(8:V) has been rarely reported. A high proportion of patients are infants and children, often with a bleeding tendency and disseminated intravascular coagulopathy (DIC). Only one-third of the de novo patients remain in the first complete remission following multiagent chemotherapy and bone marrow transplantation (BMT). Morphocytochemically, the disorder is classified as an M5, M4, or M4/M5 variant. In the presented case, with the variant t(8:19)(p11:q13), comprehensive light and electron microscopic blast cell characterization showed monocytic and granulocytic features compatible with the M4 subtype (on the monocytic predominance range of the French-American-British classification scale). Although hemophagocytosis, one of the hallmarks of the disease, was rare in our patient, numerous autophagic vacuoles were present. Immuno- and genotyping showed a myelomonocytic phenotype with no evidence of early progenitor antigen expression or mixed leukemia. These results and those of previous reports support the high specificity of t(8:16) or its variants to the unique M4/M5 type leukemia and the role of a gene on 8p11 in this specific transformation.

ALL-1 gene rearrangements in acute myeloid leukemia: association with M4-M5 French-American-British classification subtypes and young age

We have analyzed by Southern blotting the ALL-1 (MLL, HRX, Hrtx 1) gene configuration in a series of 126 patients with acute myeloid leukemia (AML) representative of all ages and French-American-British Classification groups and correlated this genetic feature with clinical and biological features at diagnosis. ALL-1 gene rearrangements were detected in 17 of the 74 cases with M4-M5 (myelomonocytic and monocytic) AML and in 2 of the 52 cases with other leukemic subtypes (P < 0.01). Within the series of 74 M4-M5 patients, ALL-1 rearrangements were significantly associated with French-American-British Classification M5 (P = 0.009), high WBC (P = 0.002), and young age. In particular, all 5 infant (< 1.5 years) AML cases, 6 of the 19 (31%) patients between 1.5 and 18 years of age, and 6 of the 50 (12%) patients > 18 years old showed an altered ALL-1 genomic configuration (P < 0.001). Immunophenotypic characterization revealed coexpression of lymphoid and myeloid markers in 6 of 17 ALL-1 rearranged M4-M5 cases. The IgH gene configuration was studied in 77 of 126 AMLs. Five patients (6%) showed IgH clonal rearrangements and all were in the ALL-1 rearranged group (P < 0.0001). Our findings indicate that ALL-1 rearrangement is the commonest genetic alteration presently detectable in M4-M5 AML, particularly in childhood where it is found in up to one-third of all cases. The association of IgH rearrangements with ALL-1 alterations in AML, coupled to the frequent detection in this subset of lymphoid associated markers, further supports the origin of these tumors from a common multipotent precursor with bipotential lymphoid and monocytic differentiation capability.

Detection of the chromosome 16 CBF beta-MYH11 fusion transcript in myelomonocytic leukemias

Karyotypic detection of chromosomal 16 abnormalities classically associated with AML M4Eo can be difficult. Characterization of the two genes involved in the inv(16)(p13q22), CBF beta and MYH11, has allowed the detection of fusion transcripts by reverse-transcriptase polymerase chain reaction (RT-PCR). We have analyzed CBF beta-MYH11 fusion transcripts by RT-PCR in myelomonocytic leukemias, with or without eosinophilia, to determine whether their presence correlates with morphology. Fifty-three cases (11 AML M4Eo; 1 AML M4 with atypical abnormal eosinophils (AML M4 "Eo"); 29 AML M4; 8 AML M5; 3 CMML; and 1 AML M2 with eosinophilia) were analyzed. All 11 typical AML M4Eo were CBF beta-MYH11 positive. The single case of AML M4 with distinctive eosinophil abnormalities was negative by karyotype, RT-PCR and fluorescent in situ hybridization (FISH). Three of 29 (10%) AML M4 without abnormal eosinophils were CBF beta-MYH11 positive, 1 of which did not show any apparent chromosome 16 abnormalities by classical metaphase analysis (2 not tested). Both cases tested also showed MYH11 genomic rearrangement. None of the other leukemias were RT-PCR positive. Follow-up of three patient showed residual positivity in apparent complete remission. These data show that CBF beta-MYH11 fusion transcripts occur not only in the vast majority of typical AML M4Eo, but also in approximately 10% of AML M4 without eosinophilic abnormalities, a much higher incidence than the sporadic reports of chromosome 16 abnormalities in AML M4 would suggest. Taken together with the detection of CBF beta-MYH11 transcripts in the absence of apparent chromosome 16 abnormalities by classical banding techniques, these data show that additional screening by either RT-PCR or FISH should be performed in all AML M4, regardless of morphologic features, to allow accurate evaluation of the prognostic importance of this fusion transcript.

[Differentiating agents in myelodysplastic syndromes. Analysis of personal cases]

The Myelo-Dysplastic Syndromes are a heterogeneous group of diseases which includes patients with different prognosis. There is no agreement about the management and the therapeutic strategy must be based on many individual parameters, particularly the age of the patients and their performance status. The therapeutic options range from no cytotoxic therapy for low-risk patients up to more aggressive treatment for high-risk patients, with disappointing results except for the very few cases eligible for allogenic bone marrow transplantation. The leukaemic cell can be induced to differentiate, so losing its self-maintenance potential; different drugs such as Interferon, vitamin D3, retinoids and arabinosyl-cytosine (low doses) have shown a differentiating action on myeloid blasts in "vitro". We summarize the general strategy in the treatment of myelo-dysplastic syndromes based on literature data, and on our results about the efficacy and tolerance of a combination of the above mentioned differentiating drugs, in a group of 27 elderly patients affected by myelodysplastic syndrome with poor prognosis. We obtained 14 objective responses (52%), and the median overall survival of these patients have been compared with that of 25 patients with severe myelodysplastic syndrome treated with a conventional regimen. In the 27 patients receiving the differentiating combination the median survival was found to be 14.7 months, versus 8.4 months for the control group. The results obtained are encouraging about the tolerance and the efficacy of this combination in elderly patients with a poor MDS prognosis. Further randomized studies are necessary to establish whether this treatment can really improve the survival in this group of patients.

Granulocytic sarcomas of small intestine and brain are associated with acute myelomonocytic leukaemia with abnormal eosinophils and inversion of chromosome 16

We report two cases of acute myelomonocytic leukaemia with abnormal eosinophils (M4Eo) in which the presenting feature was small bowel obstruction. We suggest there is a unique clinicopathological association between small intestine involvement with leukaemia and the M4Eo subtype. Central nervous system involvement by myeloblastoma occurred in one of the two cases which is a recognised feature of M4Eo and should necessitate prophylaxis with intrathecal therapy. Inversion of chromosome 16 which is a cytogenetic marker for M4Eo was demonstrable in one of the two cases.

[Acute myelomonocytic leukemia with eosinophils. Apropos of a case with a cytogenetic analysis and nosologic discussion]

Report of overwhelming leukemia with meningeal involvement in a 13-year-old. Cytologic and ultrastructural examinations showed features of myelomonocytic leukemia with abnormal eosinophils. The karyotype showed pericentric inversion of chromosome 16. Although these findings establish the diagnosis of acute myelomonocytic leukemia with abnormal eosinophils (M4Eo), this case ran an exceptionally severe course and exhibited some unusual cytologic features.

Phenotyping of acute myelomonocytic (AMMOL) and monocytic leukemia (AMOL): association of T-cell-related antigens and skin-infiltration in AMOL

Leukemic blast cells in 25 cases of AMMOL (13 cases) and AMOL (12 cases) were positive for My7 (CD13) and My4 (CD14), while only 44% reacted with LeuM3 (another CD14 MoAb). T-cell-related antigens were detected in 44% of the cases (CD2, 24%; CD4, 12%; CD7 36%). The expression of LeuM3 and TcrAg on blast and monocytic cells was mutually exclusive, with three cases expressing neither LeuM3 nor TcrAg. All six patients with myeloperoxidase negative AMOL and the TcrAG+/LeuM3- phenotype had leukemic skin infiltrations.