Contribution of immunophenotype to the classification and differential diagnosis of acute leukaemia

HLA-DPB1 supertype-associated protection from childhood leukaemia: relationship to leukaemia karyotype and implications for prevention

Most childhood B cell precursor (BCP) acute lymphoblastic leukaemia (ALL) cases carry the reciprocal translocation t(12;21)(p13;q22) ( approximately 25%), or a high hyperdiploid (HeH) karyotype (30%). The t(12;21) translocation leads to the expression of a novel fusion gene, TEL-AML1 (ETV6-RUNX1), and HeH often involves tri- and tetrasomy for chromosome 21. The presence of TEL-AML1+ and HeH cells in utero prior to the development of leukaemia suggests that these lesions play a critical role in ALL initiation. Based on our previous analysis of HLA-DP in childhood ALL, and evidence from in vitro studies that TEL-AML1 can activate HLA-DP-restricted T cell responses, we hypothesised that the development of TEL-AML1+ ALL might be influenced by the child's DPB1 genotype. To test this, we analysed the frequency of six HLA-DPB1 supertypes in a population-based series of childhood leukaemias (n = 776) classified by their karyotype (TEL-AML1+, HeH and others), in comparison with newborn controls (n = 864). One DPB1 supertype (GKD) conferred significant protection against TEL-AML1+ ALL (odds ratio (OR), 95% confidence interval (95% CI): 0.42, 0.22-0.81; p < 0.005) and HeH ALL (OR; 95% CI: 0.44, 0.30-0.65; p < 0.0001). These negative associations were almost entirely due to a single allele, DPB1*0101. Our results suggest that DPB1*0101 may afford protection from the development of TEL-AML1+ and HeH BCP ALL, possibly as the result of a DP-restricted immune response to BCP ALL-associated antigen(s), the identification of which could have important implications for the design of prophylactic vaccines.

Adult acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) in adults is a relatively rare neoplasm with a curability rate around 30% at 5 years. This consideration makes it imperative to dissect further the biological mechanisms of disease, in order to selectively implement an hitherto unsatisfactory success rate. The recognition of discrete ALL subtypes (some of which deserve specific therapeutic approaches, like T-lineage ALL (T-ALL) and mature B-lineage ALL (B-ALL)) is possible through an accurate combination of cytomorphology, immunophenotytpe and cytogenetic assays and has been a major result of clinical research studies conducted over the past 20 years. Two-three major prognostic groups are now easily identifiable, with a survival probability ranging from <10 to 20% (Philadelphia-positive ALL) to about 50-60% (low-risk T-ALL and selected patients with B-lineage ALL). These issues are extensively reviewed and form the basis of current knowledge. The second major point relates to the emerging importance of studies that reveal a dysregulated gene activity and its clinical counterpart. It is now clear that prognostication is a complex matter ranging from patient-related issues to cytogenetics to molecular biology, including the evaluation of minimal residual disease (MRD) and possibly gene array tests. On these bases, the role of a correct, highly personalised therapeutic choice will soon become fundamental. Therapeutic progress may be obtainable through a careful integration of chemotherapy, stem cell transplantation, and the new targeted treatments with highly specific metabolic inhibitors and humanised monoclonal antibodies.

Allogeneic bone marrow transplantation vs chemotherapy for children with Philadelphia chromosome-positive acute lymphoblastic leukemia

Allogeneic bone marrow transplant (BMT) with an MRD in complete remission (CR)1 is the preferred treatment for children with Philadelphia-positive (Ph(+)) ALL. The role of MUD BMT in CR1 is still controversial. We compared the outcomes of two treatment strategies: BMT using an MRD or MUD vs chemotherapy in children with Ph(+) ALL in CR1. In total, 21 children were treated from 1985 to 2001. In all, 10 received chemotherapy and 11 received allogeneic BMT: four MRD, seven MUD. In the MRD group, one relapsed 12 months after BMT and died; the remaining three are long-term event-free survivors (median follow-up, 6.1 years). In the MUD group four died; the remaining three are long-term event-free survivors (median follow-up, 7.2 years). The 4-year event-free survival (EFS) for the BMT group was 53+/-15%. In the chemotherapy group, seven relapsed after a median period of 12.5 months and three remain in continuous CR (median follow-up, 2.4 years). Four chemotherapy patients received CR2 transplants; all died. The 4-year EFS for the chemotherapy and MUD groups was 33+/-17 and 35.7+/-20%, respectively. This difference was not statistically significant. We continue to support treating children with Ph(+) ALL with MRD BMT in CR1. The effectiveness of MUD BMT vs chemotherapy merits further study.

Direct association of socio-economic status with T-cell acute lymphoblastic leukaemia in children

Lymphoblasts from 186 consecutive untreated children <18 years were analysed by flow cytometry in Brazil. Socio-economic status was defined by family income; undernourishment by height and weight for age standardised z scores below -1.28. The observed frequencies were precursor-B (pre-B) CD10 positive acute lymphoblastic leukaemia (ALL) (CD10+) 65%, pre-B CD10 negative (CD10-) 13%, and T-ALL 18%. The typical incidence peak at age 2-5 years was observed among the CD10 positive cases. Nutritional variables were not associated with immunophenotypes. Low monthly per capita income was associated with T-immunophenotype (P=0.024). In conclusion, a direct association between unfavourable socio-economic status and the T-phenotype indicates a potential role of socio-economic factors on the genesis of ALL in children, thus confirming indirect data of the international literature.

Is the timing of exposure to infection a major determinant of acute lymphoblastic leukaemia in Hong Kong?

The hypothesis that protection of infants from exposure to infectious agents with delayed first exposure to one or more specific agents together contribute to the aetiology of childhood leukaemia, especially common acute lymphoblastic leukaemia (cALL), has substantial indirect support from descriptive epidemiology and case-control studies in developed Western countries. A case-control study of childhood leukaemia diagnosed at ages 2-14 years has now been conducted in Hong Kong. Cases (n=98) formed a consecutive series of Chinese children diagnosed with acute leukaemia; controls (n=228) were identified following a survey using random digit dialling and required to attend for medical examination by a paediatrician. Interviews with mothers were conducted in hospital by one trained interviewer using a structured questionnaire. Odds ratios (OR) and 95% confidence intervals (CI) are reported for exposure variables capable of serving as proxies for exposure to infection in two critical time periods: first year of life, year before reference date (diagnosis for cases, corresponding date for controls). Analyses used logistic regression with adjustment for appropriate confounders. Change of area of residence reduced risk if during the first time period (OR = 0.47 [95% CI 0.23, 0.98]) and increased risk if during the second (OR=3.92, [95% CI 1.47, 10.46]). Reported roseola and/or fever and rash in the first year of life reduced risk (OR=0.33 [95% CI 0.16, 0.68]) whereas tonsillitis in the period 3-12 months before reference date increased risk (OR=2.56 [95% CI 1.22, 5.38]). Some other proxies for exposure to infection at the critical times were associated with predicted patterns of risk but day-care attendance failed to show predicted associations. These results provide support for the delayed exposure hypothesis in an affluent geographical setting in which population exposure to infectious agents is quite distinct from the settings of previous case-control studies.

Practical applications of immunohistochemistry in hematolymphoid neoplasms

Immunohistochemistry plays a key role in the diagnosis and classification of hematolymphoid neoplasms. New cell and lineage markers are constantly being discovered and added to the existing long list of antibodies. In this review article we provide general information and new applications of the commonly used hematolymphoid markers. We also discuss the features and applications of some newly discovered markers, such as ALK, fascin, granzyme/perforin, and tryptase. There is no universal "panel" for the diagnosis of hematolymphoid neoplasms. However, in this review article, we provide suggested panels for a given hematolymphoid neoplasm that is based on our experience and that reported in the literature.

Diagnosis and treatment of childhood acute myelogenous leukemia

Acute myelogenous leukemia (AML) accounts for about 20% of the acute leukemias seen in children. In contrast to childhood acute lymphoblastic leukemia (ALL), there has only been a modest improvement in the cure rate of children with AML during the past two decades. Approximately 40% of children treated with chemotherapy alone are long-term survivors. The outcome is somewhat better for those children who are given bone marrow transplants from histocompatible sibling donors early in the first remission. During the last decade, however, new insights into the molecular basis of AML has increased our understanding of the pathogenesis and biology of this group of leukemias and are beginning to provide us with new therapeutic strategies.

Bilineal acute leukemia of B and T lineage with a novel translocation t(9;17)(p11;q11)

We describe a case of bilineal leukemia in a 5-year old boy with a rare immunophenotype and the novel translocation t(9;17)(p11;q11) as the sole chromosomal abnormality. Two immunologically distinct blast cell subsets expressed T-markers (CD2, CD5, CD7) and common ALL markers (TdT, CD19, CD22, CD10), respectively. Both cell populations were CD34 negative. The patient, who presented with CNS leukemia, responded promptly to standard chemotherapy for lymphoblastic leukemia and remains in complete remission 20 months from diagnosis. Other translocations between chromosomes 9 and 17 have been infrequently reported in a variety of leukemias but as yet their biologic significance is unknown. The clinical course of this case suggests that t(9;17)(p11;q11) may not have an adverse influence on the disease outcome. However, the role of t(9;17) in the pathogenesis of this unusual lymphoid phenotype remains unresolved.

Clustering of childhood leukaemia in Hong Kong: association with the childhood peak and common acute lymphoblastic leukaemia and with population mixing

Incidence data of childhood leukaemia (CL) in Hong Kong (1984-90) have been analysed for evidence of variation between small areas. All cases (n=261) were classified by morphological cell type, with the majority (n=205) being acute lymphoblastic leukaemia (ALL), and haematological review has permitted immunophenotypic classification for 73% of these. The data have been examined for evidence of spatial clustering within small census areas (TPUs) and for association with population mixing, with attention focused on those subgroups (especially the childhood peak of ALL--taken here to be diagnoses in children from 24 months up to the seventh birthday--and common ALL) which, it has been hypothesized, may be caused by unusual patterns of exposure and response to common infections. For the whole of Hong Kong, there was evidence of spatial clustering of ALL at ages 0-4 years (P = 0.09) and in the childhood peak (P<0.05). When these analyses were restricted to TPUs where extreme population mixing may have occurred, overall incidence was elevated and significant evidence of clustering was found for ALL (P<0.007) at these ages and for the common ALL in the childhood peak (P = 0.032). Replication of the analyses for subsets of leukaemia that were not dominated by the childhood peak of ALL found no evidence of clustering. This is the first investigation of an association between population mixing and childhood leukaemia in Asia and the first to include clustering and to consider particular subsets. The results are supportive of the 'infectious' aetiology hypothesis for subsets of childhood leukaemia, specifically common ALL in the childhood peak.

Differential diagnosis based on immunological-phenotyping in suspected malignant bone marrow involvement in childhood

The diagnostic value of immunophenotyping (IP) as a first-line diagnostic method in diseases that infiltrate the childhood bone marrow (BM) or mimic infiltrated BM was examined. Two hundred and fifty unselected BM samples from 250 children suspected to have a malignancy infiltrating their BM were evaluated by means of IP and conventional morophological-cytochemical (MC) studies. We applied the alkaline phosphatase anti-alkaline phosphatase method for IP using a panel of monoclonal antibodies (Mabs) against leukocyte-associated antigens, neuroectodermal antigens, and intermediate filament antigens. Four cases of neuroblastoma, two cases of Ewing sarcoma, and one case of rhabdomyosarcoma were diagnosed by IP but not by MC studies. In nine cases of acute leukemia bone marrow blasts could not be ascribed to a specific lineage on the basis of blast morphology or histochemistry. Eight samples without morphological evidence of malignant infiltration revealed an increased percentage of immature B cell precursors (CD10+, TdT+) suggesting acute lymphoblastic leukemia. None of these children has developed malignant lymphoproliferative disease. Our data suggest that the immunological evaluation of BM in childhood is highly capable of discriminating between different malignant populations but it does not recognize malignancy and therefore supplements but cannot replace conventional methods for diagnosis.

Neuroblastoma presenting as acute monoblastic leukemia

PURPOSE

We report a 5-year-old boy with stage 4 neuroblastoma initially diagnosed as having acute monoblastic leukemia (FAB M5A, AMoL), based on bone marrow morphology, histochemistry, immunocytochemistry, immunophenotyping and cytogenetics, all consistent with AMoL. The patient also had circulating blasts at diagnosis. After failing initial therapy for AMoL and because of concerns about residual blasts with a clumped appearance in the bone marrow, urinary homovanillic acid (HVA) and vanillylmandelic acid (VMA) and N-myc amplification in tumor cells were evaluated and found to be positive, resulting in the diagnosis of neuroblastoma. Abdominal computerized tomography showed a left adrenal mass. A review of 10 reported cases of neuroblastoma with leukemic features showed that seven of them were misdiagnosed as having leukemia, and in six of the seven, the diagnosis of neuroblastoma was made postmortem.

CONCLUSION

Neuroblastoma may be confused with acute leukemia, even with the use of modern techniques.

Myeloid markers in adult acute lymphocytic leukemia. Correlations with patient and disease characteristics and with prognosis

BACKGROUND

The expression of myeloid markers on lymphoblasts has been associated with adverse outcome in acute lymphocytic leukemia (ALL). The purpose of the study was to analyze the experience with adults treated at the University of Texas M. D. Anderson Cancer Center with myeloid marker- (MY) positive ALL in relation to patient and disease characteristics, response to therapy, and prognosis.

METHODS

Since 1988, 64 of 162 adults (40%) with newly diagnosed ALL referred to our service had MY-positive ALL. Their characteristics and outcomes were compared with the 98 patients with MY-negative ALL. Patients were treated with the vincristine-doxorubicin-dexamethasone (VAD) regimens.

RESULTS

Patients with MY-positive ALL were significantly older (median ages, 47 years vs. 33 years; P = 0.03), had a higher incidence of CD34 antigen expression (59% vs. 36%; P < 0.01), and a lower incidence of common acute leukemia antigen expression (50% vs. 71%; P < 0.01), serum alkaline phosphatase elevation (58% vs. 83%; P < 0.01), and thrombocytopenia at diagnosis (49% vs. 69%; P = 0.02). Myeloid marker positivity, as expected, was significantly higher in null cell ALL (82%), and significantly lower in mature B-cell ALL (17%) (P < 0.01). Forty-one of 64 MY-positive patients achieved complete remission (CR) after induction therapy compared with 76 of 98 patients MY-negative disease (CR rate 64% vs. 78%; P = 0.06). With a median follow-up of 45 months, no statistical differences were observed in remission duration or survival between MY-positive and MY-negative patients, overall, and within immunophenotypic subsets (T-cell vs. others), or among subgroups with single marker (CD13, CD14, CD33, CD34) positivity. The 3-year remission duration rates were 32% for MY-negative and 40% for MY-positive patients (P not significant), and 3-year survival rates were 26% and 31%, respectively (P not significant).

CONCLUSIONS

With VAD therapy, myeloid marker positivity is not associated with significant differences in prognosis in adult ALL.

Contribution of immunophenotype in the diagnosis and classification of haemopoietic malignancies

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Usefulness of immunocytochemistry for phenotypical analysis of acute leukemia; improved fixation procedure and comparative study with flow cytometry

We investigated the phenotypes of blast cells of 53 patients with acute leukemia by a modified streptavidin-biotin alkaline phosphatase (SAB-AP) labeling technique, using a panel of monoclonal antibodies [MoAb; anti-CD11b, CD13, CD14, CD33, CD34, CD41, CD3, CD7, CD10, CD19, anti-HLA-DR, and anti-myeloperoxidase (MPO)]. The selection of an optimal fixative solution for each antigen from five options of various combinations of formalin, acetone, methanol, and/or ethanol, successfully conserved cell morphology and improved specific reaction compared with the conventional methods which used a single fixative for multiple antigens. We compared the SAB-AP results with those obtained by flow cytometry (FCM) for surface markers in each case. High concordance rates for both positive and negative results were observed for each marker. However, positive reaction for some markers (anti-CD13, CD14, CD33, and CD34) were often noted only in the cytoplasm by the SAB-AP method, indicating that combination of these two methods is essential for the precise immunophenotyping of poorly differentiated leukemia cells.

Monoclonal antibody anti-MPO is useful in recognizing minimally differentiated acute myeloid leukaemia

The enzyme myeloperoxidase (MPO) is the most specific marker of myeloid lineage. The recognition of acute myeloid leukaemia (AML) with minimally differentiation (AML-M0) is established with methods that include myeloid markers CD13/CD33 and detection of MPO in blast cells by immunological techniques or electron microscopy cytochemistry (EM). We have analysed the presence of MPO in leukaemic blast cells by conventional cytochemistry and immunological methods using a monoclonal antibody anti-MPO (CLB-MPO1) in 121 cases of acute leukaemia. The aim of the study was to investigate the sensitivity of this McAb to identify AML-M0, as CD13/CD33 can be expressed in some cases of acute lymphoblastic leukaemia (ALL) and EM cytochemistry is not always available in many laboratories. Anti-MPO was positive in all cases of AML (M1-M5) which were positive by Sudan Black B reaction in similar or higher percentage ratio for each case, although in some of them did not label with CD13/CD33 tested by IF and IPc techniques. Based on the anti-MPO positivity, 5 out of 10 cases called undifferentiated leukaemia (AUL) were reclassified as AML-M0, though 4 cases were CD13/CD33 negative. Furthermore, after analysing the anti-MPO expression among 32 cases of ALL, we had to reclassify four of them as acute biphenotypic leukaemia. We conclude that anti-MPO is a very sensitive and reliable tool in AML diagnosis and has an important role in distinguishing minimally differentiated AML and biphenotypic acute leukaemia from AUL and ALL.

Clinical relevance of acute mixed-lineage leukemias

Conflicting results have been reported in recent years concerning the incidence and prognostic relevance of acute mixed-lineage leukemias (AMLL). Among the high number of possible hybrid antigen combinations, it is important to discriminate those occurring with sufficient frequency to be of general clinical significance. In this review an approach to a classification based upon the hierarchical import of developmental antigens seen during hemopoietic differentiation is suggested. As far as the clinical relevance of AMLL is concerned, some hybrid patterns have been found to be associated with distinct characteristics in terms of clinical features at the time of presentation and poor response to treatment. For these particular types of leukemia, the time has probably arrived to design more specific therapeutic regimens.

High Ia (HLA-DR) and low CD11b (Mo1) expression may predict early conversion to leukemia in myelodysplastic syndromes

The FAB classification of myelodysplastic syndromes (MDS) has been useful in predicting prognosis; however, additional methods are required to detect patients at high risk for early conversion to acute nonlymphoblastic leukemia (ANLL). Using a panel of monoclonal antibodies to myelomonocytic surface antigens (MMSA) and flow cytometry, we studied bone marrow cells from 26 patients with MDS of all five FAB subtypes. The MMSA studied included Ia (HLA-DR), CD11b (Mo1), CD14 (Mo2, My4), CD13 (My7), and CD33 (My9). Marrows were considered "positive" for a given MMSA if the percentage of reactive cells exceeded the upper limit of the normal range. Twenty-four of twenty-six patients (92.3%) were CD13 (My7)+, suggesting that CD13 may serve as a diagnostic marker for MDS. Ten of twelve patients who developed ANLL during a median follow-up of 44 weeks were Ia(HLA-DR)+. The Kaplan-Meier estimated median time to leukemia (TTL) was 16 weeks for Ia+ patients and 88 weeks for Ia- patients (P = 0.004). All six patients who developed ANLL before 16 weeks from diagnosis were Ia+, while none of the Ia- patients converted to ANLL before 24 weeks. Nine of thirteen patients with low CD11b (Mo1) expression (< 53% reactive cells) developed ANLL, compared with only two of 11 patients with high CD11b expression (> 53% reactive cells). Kaplan-Meier estimated TTL was 29 weeks for patients with low CD11b, compared to 160 weeks for patients with high CD11b (P < 0.05). Patients who met both criteria, Ia+ and low CD11b, represented the poorest prognostic subgroup, with median TTL of 13 weeks compared with 88 weeks for the others (P = 0.017). Ia and CD11b patterns were not specific for MDS subtype, and their expression did not correlate with blast count. These data suggest that MDS patients whose bone marrow cells demonstrate high Ia (HLA-DR) and low CD11b (Mo1) expression represent a poor prognostic subgroup with short TTL. These patients may be candidates for early aggressive or investigational treatment.

Flow cytometric detection of cytoplasmic antigens in acute leukemias: implications for lineage assignment

This study aimed at optimizing the conditions for flow cytometric detection of myeloperoxidase (MPO), cytoplasmic CD3 (cCD3), and cytoplasmic CD22 (cCD22), which seem to be more reliable lineage-associated markers in acute leukemia than surface antigens. Fixation methods employing saponin as detergent resulted in accurate detection of MPO and cCD3, whereas cCD22 was detectable only after buffered-formaldehyde-acetone fixation. MPO was detected in 16/17 AML, but only in 1/6 ALL, the MPO positive ALL being also CD13 positive. MPO was detectable in 3/4 AML with T-lymphoid features; a case of myeloid antigen-positive T-ALL, however, was MPO-negative. cCD3 was expressed only in T-ALL, and five cases of lymphoid antigen-positive AML were cCD3-negative. We suggest that these flow cytometric assays are useful for the lineage assignment of poorly differentiated leukemias and contribute to the identification of truly biphenotypic acute leukemias.

Rapid diagnosis of malignancy using flow cytometry

The rapid and accurate diagnosis of childhood malignancy is important both in the planning of appropriate treatment and in relieving the inevitable family anxiety. The use of flow cytometry to analyse monoclonal antibody coated single cell suspensions is widely accepted as having increased the speed and accuracy of diagnosis in leukaemias, though its use in solid tumour diagnosis is not widely reported. Ten cases of childhood malignancy in whom the diagnosis was initially made by flow cytometry and subsequently confirmed histologically are described. The technique has a number of advantages. Only a small sample is required as the analysis is carried out on a single cell suspension, the method is rapid, a diagnosis being reached within three hours of receipt of the sample, and information is obtained on cell lineage and stage of differentiation. Diagnostic accuracy is good when compared with histological results.

Plasmacytoid monocyte proliferation associated with myeloproliferative disorders

Plasmacytoid T-cell (PTC) lymphoma is a rare clinicopathologic entity characterized by generalized lymphadenopathy in association with a myeloproliferative disorder. Hepatosplenomegaly and weight loss frequently are present. Nodal T-zone expansion by mononuclear cells with ultrastructural and immunohistochemical features typical of PTC is diagnostic. All of the five previously reported cases of PTC lymphoma coincided with or heralded the onset of a clinically aggressive myeloid leukemia. This strong association and recent immunohistochemical findings in reactive or neoplastic PTC favored a monocyte/macrophage derivation of these cells, and it has been suggested that they be renamed plasmacytoid monocytes (PM). Two additional cases of PTC lymphoma were studied at the institutions of the authors, and the findings supported the concept that PTC belong to the monocytic lineage. The disease presentation was generalized lymphadenopathy with constitutional symptoms. One patient also had hepatosplenomegaly and bilateral renal enlargement concomitantly with myelofibrosis with myeloid metaplasia that progressed within months to acute myelogenous leukemia. Similar rapid evolution of acute monoblastic leukemia occurred in the other patient. Tumor cells within subtotally effaced lymph nodes had positive findings for CD45, CD4, CD7, and LN2 and negative findings for CD3, CD8, and beta F1. Occasional cells had positive findings for CD2. One case demonstrated CD5, HLA-DR, CD71, and CD43 (Leu-22)-positive cells. The myeloid/monocyte-associated antigens CD14 and CD68 were identified in both. The tumor cells lacked the B-cell markers LN1, CD20 (L26), CD19, and CD22 and did not rearrange immunoglobulin heavy chain genes and T-cell receptor beta, gamma, and delta chain genes. The term plasmacytoid T-zone lymphoma or PM proliferation is more appropriate for this rare disease. The close association of the PM proliferation with a myeloproliferative disorder indicates that the two entities are related.

Acute undifferentiated leukemia with CD7+ and CD13+ immunophenotype. Lack of molecular lineage commitment and association with poor prognostic features

The authors studied six adult patients with acute leukemia with these unusual characteristics: unclassifiable morphology and undifferentiated cytochemistry by French-American-British (FAB) criteria; concurrent expression of CD13 (and CD33) myeloid and early T-cell CD7 immune markers; no evidence of T-cell lineage commitment as determined by T-cell receptor beta (beta), gamma (gamma), and delta (delta) chain gene rearrangement study and cytoplasmic CD3 epsilon expression; and no evidence of myeloid cell lineage commitment, as shown by absent myeloid-specific c-fms proto-oncogene expression and negative myeloperoxidase ultrastructural staining (one case). Clinically, these diagnostic features matched with a poor prognosis, being associated with refractoriness to treatment, relapse and progression of disease, antecedent hematologic abnormality, and other malignancy. These cases may represent a distinct stem cell leukemia syndrome deserving immediate recognition and a nonconventional chemotherapeutic approach.

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.

Minimal requirements for the diagnosis, classification, and evaluation of the treatment of childhood acute lymphoblastic leukemia (ALL) in the "BFM Family" Cooperative Group

Minimal requirements and their rationale for the diagnosis and the response to treatment in childhood acute lymphoblastic leukemia (ALL) were defined in the recently instituted "BFM-Family"-Group, in which the German, Austrian, Dutch, Italian, Belgian, French and Hungarian childhood leukemia study groups cooperate. ALL is defined as > or = 25% lymphoblasts in the bone marrow; for confirmation of the diagnosis and classification the criteria of the French-American-British (FAB) criteria are retained. For determination of the extent of the disease at diagnosis or relapse the criteria by the Rome Workshop [1986] are recommended: An obligatory panel of monoclonal antibodies for immunophenotyping was defined, as well as criteria for precursor B-ALL and T-ALL. Cytogenetic studies may support the diagnosis and subtyping, and are essential to identify certain patients with a high risk of treatment failure (f.i. t(9;22), t(4;11)). The role of molecular genetics for the diagnosis and the characterization of leukemia and the value of its clinical application needs further elucidation. Relapse was defined as recurrence of evident leukemia in the blood, bone marrow (> or = 25% lymphoblasts) or at any other site (to be confirmed by histological examination). Bone marrow involvement combined with extramedullary relapse was defined as > or = 5% lymphoblasts in the bone marrow.

Immune markers in hematologic malignancies

The precise delineation of biologic traits that distinguish normal hematopoietic cells from their malignant counterparts is of fundamental importance in understanding all aspects of hematologic malignancies. An increasingly sophisticated technologic battery has been utilized to dissect out these differences--primarily utilization of monoclonal antibodies, by immunoperoxidase, immunoalkaline phosphatase and flow cytometric techniques. An even more basic understanding of normal and malignant hematopoietic cells has begun to evolve as molecular biology begins to unravel gene misprogramming by Southern and Northern blot analysis and the polymerase chain reaction. These techniques not only help distinguish a normal cell from a malignant one, but characterize the malignant clone as B-lymphoid, T-lymphoid or myeloid and allow further subcategorization within these broad lineages. These distinctions are vital to the entire spectrum of basic and clinical research involving hematologic malignancies and are assuming an increasingly important role in their diagnosis, prognosis and treatment.

Monoclonal antibodies in myeloid diseases: prognostic use in acute myeloid leukaemia

Bone marrow cells from 109 patients (median age 60) with newly diagnosed acute myeloid leukaemia (AML) were prospectively immunophenotyped (IP) and the prognostic value of monoclonal antibody (MAB) reactivities was analysed to detect differences in complete remission rates and survival, not only between groups of MAB + and - bone marrow cells, but also in cases with or without prominent MAB reactivity as compared to normal BM reactivity of the respective MABs. This approach was based on the assumption that the qualitative expression of antigens is not an all or none phenomenon, but that different degrees of expression of antigens exist. Patients with significantly elevated CD13 (MY7+) cells in bone marrows (CD13 greater than reference value + one standard deviation) (S.D.) showed decreased probability of entering CR (p less than 0.05) and a significantly shorter survival (p less than 0.05). Superior CR rates (p less than 0.05) without difference in long-term survival were seen in patients with low CD33 (MY9) or low HLA-DR expression, while high CD14 (MY4) expression showed a trend towards an adverse factor (p = 0.12). No other antibody reactivities showed differences in CR rates (CD3, CD20, CDw65 (VIM-2) and NAT-9). The more prominent bone marrow expression of CD33 antigen than CD13 (CD33/CD13 greater than 1) correlated to a better chance of entering CR (p = 0.01) and to improved survival (p = 0.002), while the expression of high numbers of VIM-2+ cells was a favourable prognostic factor regarding length of survival (p = 0.002). The importance of a high CD33/CD13 ratio as a positive prognostic factor was evaluated using stratified analysis according to age or leucocyte counts at presentation. In both cases, CD33/CD13 was associated with longer survival (age: p = 0.05, leucocyte counts: p = 0.03). A Cox multiparameter analysis revealed that the CD33/CD13 ratio was a favourable prognostic factor (p = 0.03) together with age (p = 0.001) and leucocyte counts in peripheral blood (p less than 0.01). We conclude that establishing the immunologic phenotype can be of prognostic value in cases of AML, especially with regard to the relationship between the CD33 and CD13 antigens.

Clinical significance of the presence of myeloid associated antigens in acute lymphoblastic leukaemia

We have analysed the immunological characteristics of blasts from 89 acute lymphoblastic leukaemia (ALL) cases (62 adults and 27 children), by using a panel of antilymphoid and myeloid associated monoclonal antibodies (McAb) and the APAAP method, which detects membrane and cytoplasmic expression of antigens. The McAb CD19 was the marker most consistently expressed in B lineage ALL, being positive in 100% of cases, compared to CD24 and CD22 expressed in 82% and 79%, respectively. Similarly, for the T lymphoid lineage, the McAb CD3 was the most reliable and specific marker, being expressed in all T-ALL cases including those with an early thymic phenotype (CD7+, TdT+). Lymphoblasts from eight adults (12.9%) and three children (11.1%) expressed one to four myeloid associated antigens recognized by CD13, CD14, CD33 and anti-myeloperoxidase. There were no substantial clinical and morphological differences between the two ALL groups with or without myeloid associated markers. However, the presence of myeloid associated markers in adult ALL was associated with a significantly lower complete remission (CR) rate (P = 0.05) and with a shorter survival (P = 0.001); this variable was independent of advanced age and high WBC. It is concluded that immunophenotypic analysis in ALL should include myeloid markers for its probable prognostic implications.

Immunological typing of acute leukaemias by rosetting with immunomagnetic beads: comparison with immunofluorescence staining

Immunological phenotyping of acute leukaemias is important for a more precise diagnosis with respect to both cell lineage and maturation level. We have developed a rapid and reliable method for immunophenotyping, based on the use of magnetic monodisperse beads coated with monoclonal antibodies. After only a 10-min incubation of immunomagnetic beads (IMB) with mononuclear cells isolated from bone marrow or peripheral blood, the percentage of rosetting cells can be counted in the microscope. A panel of 16 monoclonal antibodies against haematopoietic cell-surface antigens was applied on 29 cases of acute myelogenic (AML) or lymphocytic (ALL) leukaemias, in order to compare immunological typing by immunomagnetic beads with immunofluorescence staining (IF). In all the cases tested, the two methods showed a virtually identical antigen distribution. The procedure described offers the advantages of being fast and simple to perform. Moreover, it has a high specificity and is easy to interpret in cases with low antigen expression.

CD7 positive acute myeloid leukaemia: a subtype associated with cell immaturity

Seventeen patients with acute myeloid leukaemia (AML) whose blasts co-expressed the T-cell associated CD7 antibody were identified among 160 consecutive AML cases. Fourteen had FAB defined AML according to morphocytochemical criteria, whereas three patients were classified as 'MO' on the basis of immunophenotype. The incidence of CD7 positively was particularly significant in the less differentiated subtypes M0 and M1 compared with other FAB groups (P less than 0.001). In all cases the myeloid determinants CD13 and/or CD33 were associated with CD7 expression. Other B-lymphoid (CD10, CD19) or T-lymphoid (CD2, surface and cytoplasmic CD3) markers were analysed and found to be negative. Five out of 15 cases examined were TdT+. Clonal rearrangements of the immunoglobulin heavy chain (IgH) and/or T-cell receptor (TcR) beta chain genes were identified in only three out of 13 cases. Among these, one out of five co-expressing TdT showed IgH rearrangement when analysed at the DNA level. Clinical features at presentation and response to induction therapy did not allow us to consider CD7+ AML patients as a distinct subgroup with prognostic significance. Our data indicate that CD7 expression is a common finding in immature AML, being generally found in the absence of other T-cell features. Rather than suggesting the occurrence of 'mixed leukaemia', such cases confirm a broader spectrum of CD7 reactivity and its possible identification of a particular subset of myeloid progenitors.

CD7-positive acute leukemia lacking T cell receptor gene rearrangements and terminal deoxynucleotidyl transferase expression suggesting pre-T cell origin

In this report, we describe a case of acute leukemia possessing a unique immunophenotype. Leukemic cells isolated from peripheral blood were analyzed by automated fluorescence-activated flow cytometry. They demonstrated the following antigen pattern: CD7+, CD38+, transferrin receptor+, HLA-DR+, common ALL antigen (CALLA)-, and terminal deoxynucleotidyl transferase (TdT)-. No expression of B cell or myeloid antigens was observed. The observed antigen pattern suggests a pre-T cell origin. In addition, the tumor cells contained germline T cell receptor beta (T beta) and gamma (T gamma) chain genes, and a germline immunoglobulin heavy chain (JH) gene. These findings support the concept that pre-T cell leukemias may demonstrate germline T beta and T gamma genes as well as lack TdT expression. In addition, our results suggest that CD7 expression may be one of the earliest events in T cell differentiation, occurring prior to both T beta an T gamma gene rearrangements, and TdT expression.

Correlations between acute lymphoid leukemia (ALL) immunophenotype and clinical and laboratory data at presentation. A study of 350 patients

The phenotypes of malignant cells from 350 untreated patients with acute lymphoblastic leukemia (ALL) were determined at diagnosis with the use of a panel of monoclonal antibodies to leukocyte antigens. According to the phenotypes seen, the cases were divided into five groups, pre-B ALL, B-ALL, T-ALL, MO-ALL, and undifferentiated ALL. Each group was subdivided, resulting in 11 defined immunologic subtypes. Correlations between clinical and laboratory features were investigated at presentation. ALL of early-B phenotype associated with elevated cell counts occurred more often in female and infant patients than in male patients. Involvement of the central nervous system was frequent in B-ALL, which occurred mostly in male patients. A male prevalence was also seen in ALL of T-lineage in which significant differences regarding clinical characteristics and leukocyte counts appeared among the four subtypes. The clinical relevance of phenotypic subcategorization is supported by our observations.

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.

Immunodiagnosis of acute leukemia displaying ectopic antigens: proposal for a classification of promiscuous phenotypes

The nature of the blast cells in 163 cases of acute leukemia was investigated by immunophenotyping, with particular emphasis on the expression of "ectopic" surface membrane structures. Although no antigen included in our panel except CD3 revealed absolute lineage restriction, immunological typing allowed a definite characterization of blast cells in more than 90% of cases. Four groups of patients were identified (A, B, C, D) with different degrees of antigen ectopic expression. We classified as group A leukemias (74%) those expressing conventional antigenic patterns, in absence of cross-lineage markers. Samples classified as group B (18%) showed a single ectopic membrane specificity, apparently discordant with the overall composite phenotype; such a "low-grade deviation" did not prevent a definite immunodiagnosis. Pattern C specimens (5%) revealed a promiscuous coexpression of markers related to different lineages (biphenotypic leukemias), whereas group D included unclassifiable phenotypes, characterized by no antigen or DR-only expression. Our findings suggest the possibility of interpreting complex phenotypic constellations of membrane markers in a consistent and logical manner.

Recent experience with intensive combination chemotherapy for treatment of childhood acute lymphoblastic leukaemia

Forty-eight children with acute lymphoblastic leukaemia (ALL) who presented to the Oncology Department of Our Lady's Hospital for Sick Children, Crumlin, Dublin over a 52 month period were treated using a schedule modified from the BFM-81 protocol. All patients achieved remission within four weeks. With a minimum follow up period of 18 months, actuarial disease free survival was 68% and overall survival 75%. Mean hospital stay throughout the treatment period was 31 days. While these results represent an improvement in overall survival compared with historical controls, careful selection of risk categories will be the major aim of future studies so that more appropriate treatment can be instituted for high risk patients while minimising therapy for low risk disease.

Immunophenotyping in the classification of acute leukemia in adults. Interpretation of multiple lineage reactivity

Fifty-nine adult patients with acute leukemia were classified using a combination of the French-American-British (FAB) criteria and characterization by immunophenotyping using flow cytometric study. The authors identified 51 patients with acute myeloblastic leukemia and eight with acute lymphoblastic leukemia. This procedure permitted lineage assignment in leukemias that otherwise might have been unclassifiable. In addition, the authors demonstrated that the leukemic blasts of 29% of patients with myeloblastic disease exhibited one or more T-cell antigens on their surface. The use of immunophenotyping has greatly enhanced the authors' ability to correctly identify the lineage of acute leukemias. The data, however, must be interpreted with caution with respect to diagnosing acute mixed lineage leukemias and must be integrated with the morphologic and cytochemical evaluation of traditional classification schemes. The possible significance of T-cell markers in myeloblastic leukemia is discussed.

Laboratory and clinical applications of monoclonal antibodies for leukemias and non-Hodgkin's lymphomas

Important insights into leukocyte differentiation and the cellular origins of leukemia and lymphoma have been gained through the use of monoclonal antibodies that define cell surface antigens and molecular probes that identify immunoglobulin and T-cell receptor genes. Results of these studies have been combined with markers such as surface membrane and cytoplasmic immunoglobulin on B lymphocytes, sheep erythrocyte receptors on T lymphocytes, and cytochemical stains. After using all of the aforementioned markers, it is now clear that acute lymphoblastic leukemia (ALL) is heterogeneous. Furthermore, monoclonal antibodies that identify B cells, such as the anti-CD20 and anti-CD19 antibodies in combination with studies of immunoglobulin gene rearrangement, have demonstrated that virtually all cases of non-T-ALL are malignancies of B-cell origin. At least six distinct subgroups of non-T-ALL can now be identified. T-ALL is subdivided by the anti-CD7, anti-CD5, and antibodies that separate T lymphocytes subsets into three primary subgroups. Monoclonal antibodies are also useful in the subclassification of non-Hodgkin's lymphoma, and certain distinct markers can be correlated with morphological classification. Although monoclonal antibodies are useful in distinguishing acute myeloid from acute lymphoid leukemias, they have less certain utility in the subclassification of acute myelogenous leukemia (AML). Attempts to subclassify AML by differentiation-associated antigens rather than by the French-American-British (FAB) classification are underway in order to document the potential prognostic utility of surface markers. Therapeutic trials using monoclonal antibodies in leukemia and lymphoma have been reported. Intravenous infusion of unlabeled antibodies is the most widely used method; transient responses have been demonstrated. Antibodies conjugated to radionuclides have been quite successful in localizing tumors of less than 1 cm in some studies. Therapy trials with antibodies conjugated to isotopes, toxins, and drugs have shown promise. Purging of autologous bone marrow with monoclonal antibodies and complement in vitro has been used in ALL and non-Hodgkin's lymphoma; preliminary data suggest that this approach may be an effective therapy and may circumvent many of the obstacles and toxicities associated with in vivo monoclonal antibody infusion.

T-cell receptor gene rearrangement and its expression in human myeloid leukemia cell lines

ML cell lines (ML-1, -2, and -3) were derived from the cells of a patient with acute myelocytic leukemia preceded by a T-cell malignant lymphoma. A deletion of chromosome 11 (11q-) was common to the affected cells in both neoplastic phases. We report here that the three ML cell lines have DNA rearrangements of the T-cell receptor (TcR)-beta and gamma-chain genes in addition to immunoglobulin heavy-chain gene rearrangement, though they do not have TcR gene messages. The findings presented here indicate that ML cell lines could be used as models for the elucidation of the bilineal nature of hematopoietic neoplastic cells, though they have a biphenotypic (myelomonocytic/T-cell) marker expression.

Routine immunophenotyping of acute leukaemias

Recent progress in immunophenotyping includes the availability of monoclonal antibodies (MAbs), knowledge of specificity and reactivity patterns of these reagents, and the technical improvements and standardization of immunofluorescence and immunocytology staining procedures, including flow cytometry. These advances have contributed significantly to the establishment of immunophenotyping as an essential diagnostic tool in the differential diagnosis of types of acute leukaemia. Immunophenotyping allows for the objective and reproducible distinction of acute lymphoblastic leukaemia (ALL) from acute myeloblastic leukaemia (AML) and of T-lineage from B-lineage ALL. Immunologically defined ALL and AML subtypes have been found to convey prognostic significance. Using cell lineage-specific and differentiation stage-specific MAbs, cases of T- and B-lineage ALL and of AML can be further classified into a number of different subtypes. Routine immunophenotyping concentrates on the diagnostic enquiry into a few major, clinically relevant subtypes; only a limited number of crucial reagents are employed that are commercially available. The simplification and standardization of discriminatory immunomarker panels make immunophenotyping a reliable diagnostic instrument for the provision of critical data to make a differential diagnosis. An effort to identify the nature and origin of the blast cells precisely, immunological typing definitely plays an important part in the multiple-marker analysis of acute leukaemia (morphology, cytochemistry, karyotyping, genotyping) for applied diagnostic and fundamental research purposes.

Assessment of the pituitary hyperplasia/neoplasia interface

The determination of the type of proliferative process in the pituitary causing clinical symptoms is quite difficult using classical morphologic techniques, including immunocytochemistry and electron microscopy. The problem is unusually difficult when the material received from the surgeon consists of 1-2 mm fragments of tissue removed from the sella turcica. Morphologic criteria were extensively discussed by other investigators in this symposium. This manuscript discusses the application of flow cytometry using formalin-fixed, paraffin-embedded tissues, in the diagnosis of pituitary lesions.

Immunological typing of acute leukemias: immunoenzymatic staining of fixed cells compared with immunofluorescence staining of unfixed cells in suspension

A panel of 14 monoclonal antibodies (McAb) against hematopoietic cell surface antigens was applied on mononuclear blood or bone marrow cells from 40 cases of acute leukemia in order to compare immunoenzymatic staining (IE) (alkaline phosphatase) of fixed cells with immunofluorescence staining (IF) of unfixed suspended cells. According to the immunological results, 25 cases were phenotyped as ALL and 15 cases as AML. Cases with blast crisis secondary to chronic myelogenous leukemia (CML-BC) were not represented in this series. In all ALL cases the two methods gave an identical antigenic distribution. In 20 our of 21 cases of non-T-cell ALL, a B-cell progenitor origin was demonstrated by a positive staining reaction with the anti-CD19 McAb AB1 or HD37, and in 10 cases additionally with the anti-CD20 McAb B1 or 1F5. In contrast to the results obtained with IF, IE revealed a poor preservation of the AB1 epitope on CD19, whereas the HD37 epitope was equally well demonstrated by both methods. In 15 cases of AML the distribution of positive versus negative cells with IE or IF was identical for all McAb except J5 (anti-CALLA) (CD10) and B1 (CD20). Thus, 10/15 AML cases expressed CALLA with IE compared to 2/15 with IF. The corresponding figures for B1 were 5/15 and 0/15, respectively. Accordingly, normal myeloid precursor cells were CALLA-positive with IE but negative with IF. The discrepancy probably reflects the fact that, whereas both intracytoplasmatic and membrane-bound antigens are exposed in IE, only the latter are in IF. If the alteration of antigenic accessibility after fixation is considered, IE can safely be used for immunophenotyping of acute leukemia.