Acute myeloid leukemia with T-lymphoid features: a distinct biologic and clinical entity

We studied the clinical and biologic features of 10 cases of acute leukemia that met standard French-American-British (FAB) criteria for acute myeloid leukemia (AML) but in which the blast cells also expressed the T-cell-associated CD2 surface antigen. All cases had greater than 3% myeloperoxidase and Sudan black B-positive leukemic blasts, and blasts from seven cases contained Auer rods. Reactivity of the cells with a panel of monoclonal antibodies (MAbs) indicated that leukemic cells in all cases expressed myeloid-associated (CD11b, CD13) surface antigens, further supporting the diagnosis of AML. However, blasts from every patient coexpressed the T-cell-associated surface CD2 and CD7 as well as cytoplasmic CD3 antigens. Blasts from five patients expressed surface CD25, whereas blasts from only one expressed surface CD3. Five patients had rearranged T-cell receptor beta-chain genes, whereas only three had rearranged T-cell receptor gamma-chain genes. This pattern of lineage-related gene expression appears to define a distinct subtype of AML with T-lymphoid features (CD2+ AML) and could reflect either aberrant gene expression in leukemic blasts or transformation of a pluripotent stem cell having a flexible pattern of gene expression. Clinically, these 10 patients presented at an older age with a higher leukocyte count and a higher frequency of lymphadenopathy than did children whose blast cells were characteristic of myeloid leukemia. Patients with CD2+ AML also had poorer responses to remission induction therapy (50% v 80% entered complete remission, P = .05). However, each of the five children who failed induction chemotherapy on AML protocols had a striking response to drug combinations usually reserved for lymphoid leukemia. We conclude that this leukemia with mixed lymphoid and myeloid characteristics is a distinct biologic and clinical entity.     

Acute mixed lineage leukemia: clinicopathologic correlations and prognostic significance

The frequency and clinical significance of acute leukemia displaying both lymphoid and myeloid characteristics was determined in 123 consecutive children using a panel of lineage-associated markers. The leukemic blasts from 18 of 95 children (19%) with the diagnosis of acute lymphoblastic leukemia (ALL) by standard diagnostic criteria expressed myeloid-associated cell surface antigens. Despite immunological evidence of lymphoid differentiation (17 CALLA + and one T cell-associated antigen +) and findings of immunoglobulin gene rearrangement, blasts from these patients reacted with one to five monoclonal antibodies identifying myeloid-associated cell surface antigens (My-1, MCS.2, Mo1, SJ-D1, or 5F1). Dual staining with microsphere-conjugated antibodies and analysis by flow cytometry confirmed that some blasts were simultaneously expressing lymphoid- and myeloid-associated antigens. Conversely, blasts from seven of 28 patients (25%) with acute nonlymphocytic leukemia (ANLL), diagnosed by otherwise standard morphological and cytochemical criteria, expressed lymphoid-associated surface antigens. Dual staining of individual blasts demonstrated simultaneous expression of myeloperoxidase (MPO) (including Auer rods) in association with either T-11, CALLA, or terminal deoxynucleotidyl transferase. Blasts from one patient with ANLL demonstrated T cell receptor gene rearrangement, while blasts from another patient demonstrated characteristics associated with T (T-11), B (CALLA and heavy-chain immunoglobulin gene rearrangement), and myeloid (MPO) lineage. There were no consistent cytogenetic abnormalities, and no patient demonstrated independent leukemic clones. Each patient with typical ALL, except for myeloid-associated antigens, achieved complete remission with conventional induction therapy for ALL. By contrast, three of the seven children with ANLL whose blasts expressed the T-11 surface antigen failed ANLL induction therapy. These three patients subsequently achieved remission with ALL therapy.     

Myeloid-associated antigen expression lacks prognostic value in childhood acute lymphoblastic leukemia treated with intensive multiagent chemotherapy

Frequency and clinical significance of myeloid-associated antigen expression in blast cells were assessed in 372 consecutive children with acute lymphoblastic leukemia (ALL). A comprehensive panel of myeloid monoclonal antibodies representing seven cluster groups showed myeloid-associated antigen expression in 61 cases (16.4%), 18 of which expressed two or more antigens. The antigens expressed comprised CD11b (8.9% of the total series), CD13 (6.5%), CD33 (3.2%), CD36 (1.9%), CD15 (1.6%), CD14 (1.3%), and CDw12 (1.1%). No significant associations were found between myeloid-associated antigen expression and the presence of known adverse prognostic features (eg, higher leukocyte count, nonwhite race, older age). Myeloid-associated antigen expression had no effect on remission induction or event-free survival for the 267 children who had been treated with the same combination of chemotherapeutic agents (P = .34). Thus, blast cell expression of myeloid-associated antigens in childhood ALL appears to lack prognostic value in the context of contemporary intensive chemotherapy.     

Immunophenotyping of acute myeloid leukaemia: Relevance of analysing different lineage-associated markers

Summary The immunophenotype of 135 previously untreated patients with FAB defined acute myeloid leukaemia (AML) was studied at diagnosis. The panel of reagents included monoclonal antibodies (MoAb) recognising myeloid-associated determinants (CD11, CD13, CD14, CD33 and others) as well as MoAb directed towards lymphoid antigens (CD7, CD10, CD19) and TdT. The results indicate that CD13 and/or CD33 are consistently expressed in AML and only rarely in ALL blasts (131/135 +ve cases, versus 4/130 in ALL). Lymphoid antigen expression was rarely detected when CD10 and CD19 were investigated in AML (0.9% and 2% +ve cases, respectively), whereas significant positivities were found for TdT and CD7 (20% and 10% respectively). Concerning FAB subtypes, two new MoAb (LAM3 and LAM7) proved very useful in the specific recognition of AML with monocytic features. The phenotype CD13+ and/or CD33+, CD9+, HLA-DR– was found to be almost exclusive for M3 AML. The response to induction chemotherapy was analysed in CD7+ and in TdT+ patients. In the latter group a statistically significant lower response rate was found with respect to TdT-ve-AML patients.     

CD66 expression in acute leukaemia

Antibodies against CD66 identify antigens from the carcinoembryonic antigen (CEA) family of proteins, which belong to the immunoglobulin gene superfamily. Despite being usually restricted to cells of myeloid or monocytic origin, CD66 expression has also been reported in blasts from children with B-cell lineage acute lymphocytic leukaemia (ALL). An analysis of the CD66 expression was undertaken in a series of acute leukaemia patients. Antigenic expression was analysed using triple combinations of monoclonal antibodies (mAbs) in forty-five patients. The CD66 Kat4 fluorescein isothiocyanate clone was purchased from Dako (Glostrup, Denmark). CD66 was expressed in 2 of 29 patients with AML (acute myeloblastic leukemia) (6.8%) and in 8 of 12 patients with B-cell lineage ALL (66.7%; P <0.001); in blast crisis (BC) of chronic myelocytic leukaemia (CML), CD66 was expressed in two patients with lymphoid BC but not in the two with myeloid BC. The co-expression of CD66 with other myeloid antigens was observed in all CD66+ ALL/Ly-BC cases tested: CD 13 in six patients, CD33 in seven and CD117 in two patients. The CD66 expression is more frequent in ALL than in AML. Furthermore, we analysed minimal residual disease (MRD) in eight patients in complete remission. CD66 expression was associated with an abnormal B-cell differentiation pattern and with increases in CD34/CD19+ cells in all but one case. These findings suggest that an aberrant expression of CD66 could be used to investigate MRD in ALL. The association between CD66 reactivity and bcr-abl in adult ALL remains to be investigated. Received: 31 May 1999 / Accepted: 10 November 1999     

Prognostic value of immunophenotyping in acute myeloid leukemia. Australian Leukaemia Study Group

The diagnostic and prognostic value of immunophenotyping with 18 murine monoclonal antibodies (MoAbs) to a variety of leukocyte differentiation antigens was assessed in 168 adults aged 15 to 60 years with acute myeloid leukemia (AML). Patients were entered on the multicentre Australian Leukaemia Study Group M4 protocol, and were randomized to receive either standard or high-dose Ara-C together with daunorubicin and etoposide as induction chemotherapy, followed by standard consolidation and maintenance therapy. Diagnostic bone marrow aspirate (152 cases) or peripheral blood samples (16) were analyzed by indirect immunofluorescence and flow cytometry. MoAbs used were directed at myeloid (CD11b, CD13, CD14, CD15, CD33, CD41), lymphoid (CD2, CD3, CD7, CD9, CD10, CD19), or stem cell (HLA-DR, CD34, c-kit receptor) antigens, as well as the leukocyte integrins CD18 and CD49e, and the transferrin receptor CD71. Of the myeloid markers, CD13 and CD33 were the most useful diagnostically (71% and 79% of cases positive, respectively), with CD11b, CD14, and CD15 less commonly positive. A minority of cases expressed lymphoid antigens, either T cell (CD2 16%, CD3 7%, CD7 28%) or B cell (CD10 2%, CD19 7%). CD34 was detected on 42% and c-kit receptor on 48%. When patients were analyzed for response to treatment, CD2, CD9, and CD14 were significantly associated with complete remission rate: cases expressing these antigens had a poorer response than negative cases. In univariate analysis, CD11b+ cases had shorter periods of remission (relative risk of relapse, 2.33; P = .003) and shorter survival (relative death rate, 1.91; P = .006). In multivariate analysis, adjusting for other prognostic factors, CD9 and CD11b were significantly predictive of shorter survival. No other marker had a significant predictive effect. We conclude that myeloid MoAbs are useful in confirming the diagnosis of AML, but their prognostic value may be limited to CD11b. Lymphoid antigen expression is a consistent phenomenon in a minority of cases of AML, but appears to have little clinical significance.     

The immunophenotype of 177 adults with acute myeloid leukemia: proposal of a prognostic score

In acute myeloid leukemia (AML) patients, a variety of clinical and biologic parameters, including phenotype, have been examined for potential value in predicting treatment response and survival. The European Group for the Immunological Classification of Leukaemias (EGIL) has proposed that AML be defined immunologically by the expression of 2 or more of the following myeloid markers: myeloperoxidase, CD13, CD33, CDw65, and CD117. With regard to this classification, the prognostic significance of 21 antigens taken separately and with immunophenotypic subgroups were evaluated and compared with other clinical and biological variables in 177 adult AML patients. None of the antigens tested were associated with treatment outcome. In contrast, patients with blasts disclosing a full expression of panmyeloid phenotype (defined by the expression of all 5 myeloid markers) had a higher complete remission rate (P <. 0001) and differed significantly in disease-free survival (P =.02) and overall survival (P =.008) than patients whose cells expressed fewer than 5 of these markers. In multivariate analysis, only age, panmyeloid phenotype, performance status, and permeability glycoprotein activity influence treatment outcome. Cytogenetics was significant in univariate analysis but not in multivariate analysis, most likely because of the redundancy with panmyeloid phenotype and a higher sensitivity of immunophenotyping. Patients whose cells exhibit the panmyeloid phenotype appear to define a relatively homogeneous biological subset of AML. The 4 independent prognostic factors were used to create a prognostic score, defined by the number of factors present. This score permitted a stratification of patients with AML, thereby allowing for the consideration of innovative therapies to improve outcome in the poorer outcome groups.     

The role of an anti-myeloperoxidase antibody in the diagnosis and classification of acute leukaemia: a comparison with light and electron microscopy cytochemistry

The enzyme myeloperoxidase (MPO) is the hallmark of the myeloid lineage. We have analysed the presence of MPO in blasts from 180 cases of acute leukaemia (103 acute myeloid leukaemia (AML) and 77 acute lymphoid leukaemia (ALL) by means of monoclonal antibodies anti-MPO and immunocytochemistry (alkaline phosphatase anti-alkaline phosphatase method). The aim of the study was to investigate the specificity and sensitivity of this marker compared with MPO cytochemistry by light (LM) and electron microscopy (EM), and with the expression of myeloid antigens. Anti-MPO was positive (greater than 3% blasts) in all but one of the 90 AML positive by LM cytochemistry. Of 13 AML cases negative by MPO cytochemistry, six showed 3-10% blasts reactive with anti-MPO and were also positive with antibodies to CD13 and/or CD33. The presence of MPO was confirmed in four of these by EM. The overall positivity of anti-MPO in AML was 92%. Anti-MPO was negative in all but two ALL (6% and 8% positive blasts). The blasts in these two cases were also CD13, CD33 and MPO positive by EM; both were thus reclassified as biphenotypic. Another two ALL reinterpreted as biphenotypic were negative by MPO cytochemistry and anti-MPO but were MPO positive by EM and with CD13 and/or CD33. We conclude that anti-MPO is a sensitive and specific early marker of myeloid blasts and should be incorporated in the routine immunophenotyping of acute leukaemia.     

交叉表达淋系和髓系相关抗原的急性白血病的生物学及临床特征研究

目的：探讨交叉表达淋系和髓系相关抗原的急性白血病患者的生物学与临床特征及预后。方法：用流式细胞术检测白血病细胞的免疫表型，根据FAB亚型和免疫标记将病例分为6组；CD7表达阳性的急性髓细胞性白血病（CD7^ AML）、CD7表达阴性的伴淋系相关抗原的急性髓细胞性白血病（CD7^-Ly^ AML）、不伴淋系相关抗原的急性髓细胞性白血病（Ly^-AML）、伴髓系相关抗原的急性淋巴细胞性白血病（My^ ALL）、不伴髓系相关抗原的急性淋巴细胞性白血病（My^-ALL）和急性杂翕生白血病（HAL）。结果：CD7^ AML组的白细胞数高于Ly^-AML组及CD7^-Ly^ AML组，诱导缓解率（16.7％）低于Ly^-AML组（71.4％），有显著差异；CD7^-Ly^ AML组与Ly^-AML组分别比较，发病年龄较高，白细胞数较高，贫血较明显，平均缓解期及平均生存期较短。结论：CD7^ AML及CD7^-Ly^ AML具有不同的临床特征，预后较差，可以看作一个独特的临床亚型。HAL与My^ ALL相比较，具有不同的临床特征，应该区别对待。     

Proliferation patterns in acute myeloid leukemia: leukemic clonogenic growth and in vivo cell cycle kinetics

Summary In a prospective study of 33 newly diagnosed patients with acute myeloid leukemia (AML), we analyzed the relationship of proliferation parameters with clinical parameters, response to induction therapy, and survival. The median follow-up was 26 months. The proliferative capacity of the leukemic progenitor cells was studied using colony-forming assays (number of colonyforming units, growth pattern, and spontaneous clonogenic growth capacity). The cell kinetic parameters of the bone marrow blasts were determined by in vivo labeling with iododeoxyuridine and subsequent flow cytometry: labeling index (LI), DNA synthesis time (T_s), potential doubling time. No or only weak relationships were observed between the experimental and clinical parameters such as age, sex, % blasts, white blood cell count, FAB subtype, cytogenetics, and % CD 34⁺ cells. This suggests that clonogenic growth and cell cycle kinetics of bone marrow blasts are independent cell biologic properties of AML. No association between the proliferation parameters and induction response rate was noticed. Analysis of the overall survival and event-free survival revealed trends to longer survival rates in patients with a belowmedian LI (7.6%) and below-median T_s value (14.3 h). These trends were more pronounced in the group of de novo AML (n=23), where the prolonged event-free survival in patients with below-median T_s reached statistical significance (p=0.02). None of the other parameters appeared significantly correlated with survival, although there was a trend to longer survival rates in patients who had no spontaneous clonogenic growth capacity (p=0.13). In conclusion, proliferation parameters in leukemic cells provide additional information on the cell biologic characteristics of AML, and these parameters may have prognostic value for response and duration of survival in AML.     

Characterization of childhood acute leukemia with multiple myeloid and lymphoid markers at diagnosis and at relapse

To define the clinical and biologic significance of childhood acute mixed-lineage leukemia diagnosed by stringent criteria, we studied 25 cases of acute lymphoblastic leukemia expressing greater than or equal to 2 myeloid-associated antigens (My+ ALL), and 16 cases of acute myeloid leukemia expressing greater than or equal to 2 lymphoid associated antigens (Ly+ AML). These cases represented 6.1% of 410 newly diagnosed ALLs (two treatment protocols) and 16.8% of 95 AMLs (two protocols). T-lineage--associated antigens were identified in 9 of the My+ ALL cases and in 14 of those classified as Ly+ AML; all but 1 of the 19 cases that could be subclassified had an early thymocyte stage of differentiation. The My+ ALL cases had an increased frequency of French-American-British (FAB) L2 morphology (36%); the Ly+ AML cases were characterized by FAB M1 or M2 morphology, low levels of myeloperoxidase reactivity and combined populations of myeloperoxidase-positive large blasts and small blasts generally of hand-mirror morphology. Karyotypic abnormalities included t(9;22)(q34;q11) in three cases of My+ ALL, 11q23 translocations in two cases of My+ ALL, and 14q32 translocations in three My+ ALL and five Ly+ AML cases. Mixed-lineage expression lacked prognostic significance in either ALL or AML; however, the findings indicate that some patients with Ly+ AML may respond to prednisone, vincristine, and L-asparaginase after failing on protocols for myeloid leukemia. At relapse, two My+ ALLs had converted to AML and two Ly+ AMLs to ALL; one case in each group showed complete replacement of the original karyotype. Acute mixed-lineage leukemia does not adequately describe the heterogeneity of the cases identified in this study and should be replaced by a set of more restrictive terms that indicate the unique biologic features of these leukemias.     

Osteopontin is a prognostic factor for survival of acute myeloid leukemia patients

Osteopontin (OPN) is a glycoprotein that is secreted by osteoblasts and hematopoietic cells. OPN suppresses the proliferation of hematopoietic stem cells in vitro and may regulate the hematopoietic stem cell pool. Increased serum OPN concentrations occur in chronic myeloid leukemia, multiple myeloma, and acute myeloid leukemia (AML). In the present study, we analyzed the prognostic impact of OPN in AML by investigating the expression and relevance of OPN in newly diagnosed AML patients from 2 large study groups (the German AML Cooperative Group and the Dutch-Belgian Hematology Oncology Cooperative group). IHC (n = 84), ELISAs of blood/BM sera (n = 41), and microarray data for mRNA levels (n = 261) were performed. Expression of OPN protein was increased in AML patients both in BM blasts (IHC) and in BM serum (ELISA) compared with healthy controls. Patients expressing high levels of OPN within the BM (IHC) experienced shortened overall survival (OS; P = .025). Multivariate analysis identified karyotype, blast clearance (day 16), and the level of OPN expression as independent prognostic factors for OS. This prompted us to analyze microarray data from 261 patients from a third cohort. The analysis confirmed OPN as a prognostic marker. In summary, high OPN mRNA expression indicated decreased event-free survival (P = .0002) and OS (P = .001). The prognostic role of OPN was most prominent in intermediate-risk AML. These data provide evidence that OPN expression is an independent prognostic factor in AML.     

In situ RHAMM protein expression in acute myeloid leukemia blasts suggests poor overall survival

Treatment options for patients with high-risk acute myeloid leukemia (AML) include high-dose chemotherapy regimens in combination with allogeneic hematopoietic stem cell transplantation, which takes advantage of the donor T-cell-mediated graft-versus-leukemia effect. Together with beneficial responses observed in assays targeted at leukemia-associated antigens (LAA), this encouraged research on cancer vaccines and adoptive cellular therapies in AML. The receptor for hyaluronic acid-mediated motility (RHAMM, CD168) was identified as one of the most promising LAA in AML. Thus far, little is known about in situ expression in leukemic bone marrow blasts or the prognostic role of RHAMM and its interaction partners in AML. We immunohistochemically analyzed the expression and prognostic significance of RHAMM on trephine bone marrow biopsies from 71 AML cases that had been evaluated for cytogenetics and presence of FLT3-internal tandem duplications and NPM1 mutations. Fifty-five patients (77%) were treated with curative intent, while 16 (23%) received the most appropriate supportive care. Twenty of 71 (28%) AML cases were considered RHAMM+. Receiver operating characteristic curves showed significant discriminatory power considering overall survival (OS) in AML patients treated curatively for RHAMM (p = 0.015). Multivariable analysis revealed that expression of RHAMM in >5% of leukemic blasts identifies a subgroup of curatively treated cases with adverse OS independent of failures to achieve complete remission. RHAMM not only represents a promising LAA with specific T-cell responses in AML but, if assessed in situ on blasts, also a probable prognostic factor.     

Acute myeloid leukaemia expressing the leucocyte integrin CD11b — a new leukaemic syndrome with poor prognosis: result of an ECOG database analysis

While assessing the prognostic implications of immunophenotyping in 382 patients enrolled in treatment protocols of the Eastern Cooperative Oncology Group (ECOG) for de novo adult acute myeloid leukaemia, we identified 95 patients with a unique antigen profile characterized by high expression of the leucocyte integrin CD11b (CD11b⁺ AML). High expression of CD11b was defined as 32% positive blasts based on the retrospectively established prognostic cut-off point for this antigen. Although CD11b is normally expressed by mature monocytes, natural killer cells and granulocytes, leukaemic blasts in CD11b⁺ AML lacked other immunologic monocytic features (e.g. CD14 and CD122, the interleukin-2 receptor β chain) and demonstrated a high degree of immaturity, as reflected by a high incidence of blasts expressing the stem cell factor receptor, CD117, and few blasts positive for the myeloid differentiation antigen CD15. Furthermore, by FAB criteria, only 41% of CD11b⁺ AML cases were classified as M4/M5. Patients with CD11b⁺ AML had a low response rate (54%) when compared with acute monocytic leukaemia (AMOL; 82%, P  = 0.006) or AML overall (68%, P  = 0.031), independent of age, cytogenetic abnormalities and P-glycoprotein expression. Because of its poor prognosis, recognition of CD11b⁺ AML is clinically warranted and, given its morphologic and cytogenetic ambiguity, must be based on the unique antigen profile.     

Adult precursor T-lymphoblastic leukemia/lymphoma with myeloid-associated antigen expression is associated with a lower complete remission rate following induction chemotherapy

Prognostic studies of T-cell lymphoblastic leukemia/lymphoma (T-ALL) have been performed in small patient cohorts with conflicting results. We systematically reviewed 67 adult T-ALL patients diagnosed and treated at our institute to identify clinical and pathologic prognostic factors. The median initial WBC was 21.3 x 10(9)/l. Blasts expressed at least one myeloid-associated antigen in 33%. Karyotypes were abnormal in 32% of the cases. Fifty-six of 64 patients (88%) achieved complete remission (CR). In univariate analysis, age, gender, initial WBC, CD10, CD34 and abnormal karyotype did not predict CR. Patients expressing at least one myeloid-associated antigen had a CR of 74% compared to 94% (p = 0.04) for those not expressing myeloid antigens. None of the above factors affected relapse-free or overall survival in this cohort. Our study indicates that expression of myeloid-associated antigens is associated with a lower CR rate in adult T-ALL and may be considered in risk stratification for induction chemotherapy.     

The generation of immunocompetent dendritic cells from CD34+ acute myeloid or lymphoid leukemia cells

The ability of CD34+ leukemic cells to differentiate to dendritic cells (DCs) was investigated in 18 acute myeloid leukemia (AML) and 4 lymphoid leukemia (ALL) patients. The generation of DCs was determined by the expression of DC-associated CD1a or CD83 (more than 30%) with costimulatory molecules, by CD80 antigens (>20%), and by the exhibition of allostimulatory activity. In the AML patients, allostimulatory mature DCs were generated from 3 of 9 M0 or M1, 2 of 5 M2,2 of 4 M4 or M5, and 3 of 4 ALL (L2) cases. In total, DCs were more efficiently induced from cases expressing over 75% of CD34+ among whole bone marrow mononuclear cells (8 of 12), compared with those under 75% (2 of 10; P < .05). B-cell (CD19), natural killer (NK)-cell (CD56), or T-cell (CD7) lineage markers, which were aberrantly expressed on the blasts, were rarely found on leukemic DCs at the end of the culture period, and myeloid (CD13, CD33), not lymphoid (CD10), markers were shown on ALL-derived DCs. In Philadelphia chromosome-positive ALL or AML patients with t (8;21), DCs were confirmed to be of leukemic origin by fluorescence in situ hybridization analysis.     

Flow cytometric scoring system (FCMSS) assisted diagnosis of myelodysplastic syndromes (MDS) and the biological significance of FCMSS‐based immunophenotypes

In the myelodysplastic syndromes (MDS), the haematopoietic cells show various levels of abnormal maturation and differentiation, which can be detected by flow cytometry. Testing the anomalies of stage‐ or lineage‐specific surface antigens in CD34⁺ blasts can distinguish MDS from non‐clonal cytopenic diseases, and also reflect the pathological characteristics of MDS as a class of clonal diseases for providing new clues to basic research. The present study established a flow cytometric scoring system (FCMSS) based on theproportion and antigenic co‐expression of CD34⁺ blasts. This FCMSS showed good sensitivity and specificity (77·8% and 100%) in the assisted diagnosis of low‐risk MDS without chromosome anomalies, ringed sideroblasts and excess marrow blasts. Moreover, we explored and reported different modes of abnormal expression of CD34⁺ blasts antigens in different disease stages and analyzed the biological significance of the immunotypes for the first time. We found expression of mature myeloid antigens and lymphoid antigens gradually decreased, and early functional antigens gradually increased from low‐risk MDS with normal karytype to low‐risk MDS with abnormal karyotype then to high‐risk MDS. The patients with higher FCM scores were generally accompanied with HLA‐DR15 allele or hypocellular marrow. Evolution of clones and immunological factors might have influence on expression of antigens in CD34⁺ blasts.     

Unusual immunophenotypes in acute leukaemias: incidence and clinical correlations

The incidence and clinical implications of unusual patterns of expression of leucocyte differentiation antigens in acute leukaemia were assessed on 568 newly diagnosed paediatric and adult cases undergoing immunophenotyping with a panel of monoclonal antibodies at a single centre. Among patients with the precursor B (common) form of acute lymphoblastic leukaemia (ALL), the major variant seen was the group of 15 cases with expression of myeloid surface antigens. 4.5% of ALL cases tested with antibody to CD-11b were positive, 5.1% were CD-13+, and 10.8% CD-33+. All 15 patients achieved a complete remission with chemotherapy, with six of eight children and four of seven adults remaining disease free. A smaller proportion (1.5%) of precursor B ALL patients showed expression of the T lineage marker, CD-7. The only significant variant seen in the precursor T-ALL group was expression of HLA-DR antigen, which was found in five of 35 cases; although all responded to treatment, only one remains a disease-free survivor. Among patients with acute myeloid leukaemia (AML), expression of the lymphoid markers terminal transferase (TdT) and CD-7 were commonly seen (22.2% and 28.4% respectively of cases tested). Other lymphoid markers detected on AML cases were CD2 (11.1%), CD-10 (1%) and CD-19 (4.4%). These results confirm that examples of lineage infidelity are regularly seen in large series of patients with acute leukaemia. Prospective studies using uniform treatment protocols are required to establish whether these patients have significantly different disease outcomes.     

C-kit receptor (CD0117) expression in acute leukemia

The murine monoclonal antibody YB5.B8 (CD117) identifies a transmembrane tyrosine kinase receptor encoded by the human c-kit proto-oncogene. In this study we investigated the expression of c-kit on different types of acute leukemia to determine the degree of specificity and sensitivity of this marker for the myeloid and lymphoid lineages. C-kit was positive in over half of the 115 cases of acute leukemia studied. Overall, two thirds of AML cases expressed c-kit, whereas only one of 23 ALL patients was c-kit positive. C-kit was also positive in 16 of 19 cases of myeloid blast crisis of myeloproliferative disorders and negative in four with a lymphoid phenotype. There was no correlation between c-kit expression and the degree of myeloid differentiation by FAB subtypes or other markers. We conclude that c-kit is a specific marker for the myeloid lineage, which is expressed early during hematopoietic differentiation and can aid the diagnosis of AML in difficult cases. More patients need to be tested to establish whether the expression of c-kit may define AML subgroups of prognostic significance.