Correlation of morphological FAB classification and immunophenotyping: value in recognition of morphological, cytochemical and immunological characteristics of mixed leukaemias

Acute promyelocytic leukemia M3: cytomorphologic, immunophenotypic, cytogenetic, and molecular variants

Acute promyelocytic leukemia (APL) M3 is an acute myeloid leukemia (AML) subtype characterized by proliferation of malignant promyelocytes with mature myeloid immunophenotype and the translocation t(15;17)(q22;q11), which results in the fusion of retinoic acid receptor-alpha (RARalpha) gene on chromosome 17 and the gene PML on chromosome 15. There are three M3 morphologic variants: the typical hypergranular form and the microgranular and basophilic variants. Although most leukemic cells in M3 patients express t(15;17), other cytogenetic abnormalities have also been reported. Also, there are three molecular variants of the PML/RARalpha transcript (bcr1, bcr2, bcr3). Blasts had typical hypergranular appearance (13 patients) with a mature myeloid immunophenotype (HLA-DR(-),CD13(+), and/or CD33(+)) (10 patients) in the majority of patients with M3 followed in this study. The typical translocation [t(15;17)(q22;q11)] was detected by cytogenetic analysis in 5 M3 patients, but PML/RARalpha was positive in 13 out of 15 patients, as assessed by RT-PCR (8 patients with bcr1 and 5 with bcr3 subtype). Cytogenetic diversity was found in three patients (1 with t(17;17), 1 with +8, and 1 with add (7)(q22); -7; +8). According to many studies, leukemic cell heterogeneity in APL influences the clinical outcome of disease. The analysis of certain leukemic cell characteristics on the clinical outcome in our study revealed that patients with bcr3 had shorter medians of first remission and survival in comparison to patients with the bcr1 isoform of PML/RARalpha. Also, the clinical relapse of disease in 4 APL patients with reverted PML/RAR alpha positivity is consistent with the view that detection of PML/RARalpha by RT-RCR in patients in remission implies a poor prognosis. On the contrary, lack of detection of PML/RARalpha by RT-PCR at least three times is a sign of long remission and survival.

Immunophenotypic analysis of acute lymphocytic leukemia

Acute lymphoblastic leukemia (ALL) is one of the most common hematologic malignancies. Flow cytometry is an integral part of ALL diagnosis and also provides significant patient prognostic information. This article is a practical review of the basic principles of the flow cytometric evaluation of acute leukemias, the interpretation of flow cytometric data, and the management of practical problems such as aberrant antigen, hematogones, bone marrow regeneration, and minimal residual disease.

Double immunoenzymatic APAAP staining for the detection of leukemia-associated immunophenotypes

Detection of unusual or aberrant cell immunophenotype with flow cytometry is the basis for the immunologic recognition of minimal residual disease (MRD) in patients with acute leukemia (AL). In this study, we have shown that the double immunocytochemical alkaline phosphatase antialkaline phosphatase (APAAP) staining technique also makes possible the detection of leukemic cells with unusual (leukemic) combinations of antigens (ULCA) both at diagnosis and during follow-up of patients with ULCA+ AL. The applicability of double APAAP was analyzed on bone marrow (BM) samples obtained from 12 patients (8 with AML, 3 with ALL, and 1 with undifferentiated acute leukemia [AUL]) randomly chosen from a larger group of 22 ULCA+ patients treated at our center in a 3-year period (22% observed ULCA+ AL frequency). The percentages of ULCA+ BM cells before chemotherapy were in the range of 5%-60%, which dropped to 0%-7% in 10 patients who achieved remission (range 0%-7%, p < 0.01). However, these cells could also be found 60 days after the initiation of therapy, ranging from 0%-2% of all nucleated cells. In 2 of 10 patients who achieved remission, 2% ULCA+ BM cells were found on days 35 and 60 after initiation of chemotherapy, and this finding was followed by relapse on days 110 and 270. However, the other 8 patients remained in remission despite positive finding of ULCA+ BM cells ranging from 0.2%-2% on at least one occasion. In 2 patients with AML FAB-M3 and cytomorphologic remission, the finding of ULCA+ cells by double APAAP correlated with the molecular finding of PML/RARalpha junction. These results indicate that double APAAP staining can identify leukemic cells in samples with a cytomorphologic pattern consistent with remission, but its applicability in detection of MRD awaits additional studies on a larger number of patients with ULCA+ AL.

Adult acute leukemia

Untreated acute leukemia is a uniformly fatal disease with a median survival time shorter than 3 months. Current treatment strategies provide a significant increase in survival time for most patients, some of whom may be cured. The majority of patients with acute leukemia, however, ultimately die of the disease or complications of treatment. The effective treatment of acute leukemia requires (1) differentiation of acute myeloid leukemia (AML) from acute lymphoblastic leukemia (ALL) and recognition of clinically relevant subtypes; (2) identification of patients who are more likely or less likely than average to benefit from a conventional treatment; and (3) selection of therapy that provides a reasonable likelihood of response with acceptable risk of toxic effects. The diagnosis of acute leukemia is established in most cases by a bone marrow aspirate that demonstrates at least 30% blast cells. The traditional criteria to distinguish between AML and ALL rely on morphology and cytochemical reactions. Immunologic analysis of antigen expression and analysis for numerical or structural chromosomal abnormalities of leukemia cells are routinely feasible. Karyotypic analysis is of prognostic importance and should be performed on all diagnostic specimens of bone marrow aspirate. Immunophenotypic analysis may be useful to confirm the disease classification in selected cases. The importance of the routine immunophenotypic characterization of acute leukemia, however, is controversial. The subtypes that must be recognized because of the need for specific treatment include (a) acute promyelocytic leukemia (APL), which is the M3 subtype of AML, and (b) the L3 subtype or mature B-cell ALL. Induction therapy for acute leukemia is treatment intended to achieve induction of complete remission (CR). Complete remission is defined as the absence of morphologic evidence of leukemia after recovery of the peripheral blood cell counts. Failure to achieve CR may be attributed to death during chemotherapy-induced bone marrow hypoplasia or to drug resistance manifested either as failure to achieve hypoplasia or as persistent leukemia after recovery from hypoplasia. Postremission therapy is treatment administered in CR to prevent or delay relapse of the leukemia. However, the majority of patients have disease relapse. Intensification of therapy is a treatment strategy designed to overcome resistance to chemotherapy. Recent clinical trials of intensified induction or postremission therapy suggest improved outcome. However, the toxic effects of dose intensification can be substantial, limiting any potential benefit of this approach. Identification of prognostic factors may allow one to estimate the likelihood of an outcome, to determine an optimal treatment strategy. It is well established that age at the time of diagnosis, leukemia cell karyotype, and whether the leukemia is de novo or secondary are factors that influence treatment decisions. Patients with favorable prognostic factors should probably receive conventional therapy. Patients with unfavorable prognostic factors have shown little benefit from conventional therapy. In addition, factors that indicate poor outcome with conventional therapy are also predictive of poor outcome with intensified therapy. Consequently, these patients should be considered for investigational therapeutic strategies. The bias may be to counsel them to accept the potential increased morbidity of such treatment before there is definite evidence of the possibility of improved outcome. Induction chemotherapy for younger patients with AML (less than 55 years of age) in general consists of one or more courses of cytarabine (ara-C) and an anthracycline or an anthracycline derivative. Randomized trials have failed to confirm that treatment with either etoposide or high-dose ara-C induces disease remission. Patients with secondary AML, high levels of CD34 antigen expression, or an unfavorable karyotype, however, may benefit from ind

Phenotype, genotype and cytokine production in acute leukemia involving progenitors of dendritic Langerhans' cells

To date no hematopoietic progenitors of dendritic Langerhans' cells (DLC), which represent an highly efficient class of antigen presenting cells, have been identified or the cytokines they elaborate have been defined. Here we describe an acute leukemia patient whose blasts (90-96% in peripheral blood and bone marrow) had a phenotype consistent with putative progenitors of DLC. The patient was treated with ara-C and VP-16 but did not achieve remission. The blasts had lobulated nuclei, no cytoplasmic vacuolation or Auer rods and were weakly positive for acid phosphatase and non-specific esterase and negative for PAS, granzyme A, dipeptidyl aminopeptidase IV, ATPase/ADPase and lysozyme production. The blasts were positive for CD1a, CD4, CD16, CD35, HLADR, HLADQ, CD11b, CD11c, CD14, CD33, CD34, CD11a, CD71, CD19, CD25, IL-2R beta and negative for CD2, CD7, CD8, CD10, CD22, CD56, CD57, surface or cytoplasmic CD3, TCR delta and TCR beta, HTLV-1p19 and P-glycoprotein. On liquid culture with or without 5 x 10(-9) M 12-O-tetradecanoylphorbol-13-acetate (TPA) for 3 days, the blasts formed aggregates of proliferating and elongating cells on the wall of the flasks with a decline in CD34, numerous dendritic processes appeared on the cells and there was strong positivity for ATPase/ADPase, but no other changes in phenotype. No macrophages were observed, indicating derivation from separate DLCs. Cytogenetic analysis showed chromosomal abnormalities and electron microscopy showed Birbeck granules. Southern blotting of DNA showed rearrangement of one allele for both JH and TCR beta but no HTLV-1 related sequences. Culture supernatants from blasts cultured with or without TPA showed the production of large amounts of IL-8, IL-6, TNF-alpha, MIP-1 alpha, IL-10 and interferon gamma and modest amounts of IL-1 alpha, GM-CSF and stem cell factor. The presence not only of CD1a, HLADR, HLADQ and many other characteristics including Birbeck granules, but also differentiation along the lines of DLC with appearance of dendritic processes on the cells and expression of ATPase/ADPase activity, indicate that the leukemic blasts in our patient represented a leukemic counterpart of normal progenitors of DLC and the leukemia a new entity which could possibly be classified as AML-M8. Lastly, many pro-inflammatory cytokines produced by DLC could contribute to inflammation and IL-10 to immunosuppression.

Possibilities and limitations of cytochemical methods in diagnosis of acute leukemia

Accurate identification and classification of leukemic blast cells is a very important prerequisite of the precise diagnosis of acute leukemia and has a great impact on therapy and prognosis. The purpose of this review is to consider, in the broad sense of the word, the present possibilities and limitations of enzyme cytochemistry and to emphasize how cytochemistry may contribute, on integration with the other methods of study, to the final classification and differential diagnosis of acute leukemia, a highly variable hematological disorder. In this review, the role of conventional enzyme cytochemistry, either dominant or subsidiary, in the discrimination of acute leukemia subtypes is discussed. The survey confirms the absolute necessity of immunologic marker analysis in the accurate diagnosis of acute lymphoblastic leukemia, undifferentiated or minimally differentiated leukemia and mixed-lineage leukemia because in these cases, the cytochemical evaluation provides insufficiently relevant information regarding blast cell origin, specificity of leukemia subtypes and the discrete stages of leukemic cell maturation. On the other hand, cytochemical investigation is appreciated to be dominant over immunophenotyping in characterizing acute myeloid leukemia, because of the lack of specificity of the majority of immunological markers against myeloid antigens and, because of the availability of standardized and sufficiently specific cytochemical reactions. The cytogenetic, molecular biological and electron microscopic studies mentioned in this review supplement the important information for correct differential diagnosis of acute leukemia. The prognostic impact of enzyme cytochemistry in correlation to other methods is evaluated.