Phenotyping of malignant hematopoietic cells

Summary 1255 cases of leukemia-lymphoma were tested between 1972 and 1984 by multiple marker analysis. Routine leukemia phenotyping was performed using standard morphological and cytochemical techniques in combination with clinical and histo-pathological information; the main emphasis was put on immunological surface marker analysis using erythrocyte rosette assays, TdT and a large panel of poly- and monoclonal antibody tests. The 1255 cases were divided into these major types and subtypes: 349 cases of ALL and related immature T- and Burkitt-lymphomas (cALL, pre B-ALL, B-ALL and Burkitt-lymphomas, T-ALL and immature, mostly leukemic T-lymphomas, Null-ALL), 454 cases of mature T- and B-cell malignancies (T-CLL, mycosis fungoides, Sezary-syndrome, T-lymphomas, B-CLL, hairy cell leukemia, multiple myeloma, B-lymphomas), 263 cases of acute myeloid leukemias (AML, AMMoL/AMoL), 182 cases of chronic myeloid leukemias (CML in chronic phase, CMoL, CML in blast crisis), 6 cases of erythroleukemia and 1 case of megakaryoblastic leukemia. A simplified classification scheme which has been used in our laboratories is presented. Phenotyping is of diagnostic, prognostic and therapeutic relevance, most evidently for patients with ALL. Routine leukemia phenotyping should be performed with highly standardized techniques and reagents and by combining information from several fields in the multiple marker analysis. New areas of leukemia research might become very useful for the routine procedure of phenotyping.Abbreviations ALL acute lymphoblastic leukemia - AML acute myeloblastic leukemia - AMMoL acute myelomonoblastic leukemia - AMoL acute monoblastic leukemia - cALL common ALL - CLL chronic lymphocytic leukemia - CML chronic myelocytic leukemia - CML-BC CML in blastic crisis - CMoL chronic monocytic leukemia     

Differentiation patterns in the blastic phase of chronic myeloid leukemia

The surface antigen phenotype of 30 patients with the blast phase of chronic myeloid leukemia (CML) was determined using a panel of monoclonal antibodies recognizing differentiation antigens of normal myeloid, erythroid, megakaryocyte, and lymphoid cells. Ten patients' cells expressed a phenotype corresponding to an immature myeloid cell and were felt to have "myeloid" blast crisis. None of these myeloid leukemias were TdT+ or responded to vincristine (V) and prednisone (P). Eleven patients expressed a phenotype similar to acute lymphoblastic leukemia cells and probably reflect maturation to an early B lymphocyte. All of these "lymphoid" leukemias were TdT+, and 67% of evaluable patients had a complete response to V and P. One leukemia had the phenotype of an erythroleukemia, one patient's cells expressed the phenotype of megakaryoblastic leukemia, and one leukemia had populations of both myeloid and lymphoid blasts. Six leukemias did not express surface markers characteristic of any lineage and were termed "undifferentiated." This group was heterogeneous with respect to TdT expression, but no patient had a complete response to V and P. Determination of surface antigen phenotype in CML blast crisis thus provides clinically useful information for the structuring of treatment protocols.     

Myeloid lineage specificity and high sensitivity of monoclonal antibody GM 58/8 proves its usefulness as a diagnostic reagent in acute leukemia

Monoclonal antibody (MoAb) GM 58/8 was earlier reported to be directed against an antigen expressed by myeloid progenitors (CFU-GM), myeloid precursors, granulocytes, and monocytes. Immunophenotyping of 216 cases of acute leukemia [acute myeloblastic leukemia (AML) = 147 and acute lymphoblastic leukemia (ALL) = 69] and 18 cases of chronic granulocytic leukemia in blast crisis (CGLBC) with this antibody showed that GM 58/8 reacted with 92% of AML cases (M1-M5) and 100% of myeloblastic crisis in CGL cases. All cases of ALL, lymphoblastic crisis in CGL, erythroleukemia, and erythroblastic crisis in CGL were unreactive with GM 58/8. The antibody revealed the myeloid phenotype in an additional 15 cases of otherwise unclassifiable acute leukemia and six cases of CGLBC. Eleven cases of acute "mixed lineage" leukemia were also diagnosed with the help of GM 58/8. The high specificity (100%) and sensitivity (92%) of MoAb GM 58/8 for myeloblastic leukemia is unmatched by almost all previously described myeloid MoAb and proves its usefulness as a single diagnostic reagent for AML and myeloblastic crisis in CGL.     

Acute lymphoid leukemias following either a previous chronic myelogenous leukemia or myelodysplastic syndrome: Phenotypic and genomic differences

We have analyzed the immunological and genomic characteristics of the lymphoid blast cells present in secondary lymphoid leukemias following either a previous chronic myelogenous leukemia (CML) or myelodysplastic syndrome (MDS). Twenty-one of 107 secondary leukemias analyzed displayed a lymphoid phenotype (15 after a CML and 6 after a MDS). Most of the lymphoid blast crises of CML (73%) correspond to pure lymphoid transformation, all of them having a common acute lymphoblastic leukemia (ALL) phenotype (CD10+). By contrast, in all MDS cases, lymphoid blast cells coexisted with another myeloid component (hybrid leukemias) and showed an early B phenotype. IgH and TCR-γ gene rearrangements were detected in the CML-lymphoid blast crisis (86% of cases) more frequently than in the MDS transformations (33%). The TCR-β gene was in germ line configuration in all cases while TCR-δ gene rearrangements were detected in four cases, all of them corresponding to a previous diagnosis of CML. These results show the existence of both immunophenotypic and genomic differences between the lymphoid transformations of either CML or MDS, which could reflect differences at the stage of maturation of the target cell in these transformations.     

Rapid and selective death of leukemia stem and progenitor cells induced by the compound 4-benzyl, 2-methyl, 1,2,4-thiadiazolidine, 3,5 dione (TDZD-8)

Leukemia is thought to arise from malignant stem cells, which have been described for acute and chronic myeloid leukemia (AML and CML) and for acute lymphoblastic leukemia (ALL). Leukemia stem cells (LSCs) are relatively resistant to current chemotherapy and likely contribute to disease relapse and progression. Consequently, the identification of drugs that can efficiently eradicate LSCs is an important priority. In the present study, we investigated the antileukemia activity of the compound TDZD-8. Analysis of primary AML, blast crisis CML (bcCML), ALL, and chronic lymphoblastic leukemia (CLL) specimens showed rapid induction of cell death upon treatment with TDZD-8. In addition, for myeloid leukemias, cytotoxicity was observed for phenotypically primitive cells, in vitro colony-forming progenitors, and LSCs as defined by xenotransplantation assays. In contrast, no significant toxicity was observed for normal hematopoietic stem and progenitor cells. Notably, cell death was frequently evident within 2 hours or less of TDZD-8 exposure. Cellular and molecular studies indicate that the mechanism by which TDZD-8 induces cell death involves rapid loss of membrane integrity, depletion of free thiols, and inhibition of both the PKC and FLT3 signaling pathways. We conclude that TDZD-8 uses a unique and previously unknown mechanism to rapidly target leukemia cells, including malignant stem and progenitor populations.     

Adenosine deaminase and ecto-5''-nucleotidase activities in various leukemias with special reference to blast crisis: significance of ecto-5''-nucleotidase in lymphoid blast crisis of chronic myeloid leukemia

Adenosine deaminase (ADA) and ecto-5'-nucleotidase (5'-N) activities were examined in peripheral leukocytes from patients with leukemias, including nine patients with chronic myeloid leukemia (CML) in blast crisis. Four of none cases of CML in blast crisis were myeloid and the remaining lymphoid morphologically. The diagnosis of CML in lymphoid blast crisis was further contributed by the measurement of terminal deoxynucleotidyl transferase (TdT) activity. In all four cases of lymphoid blast crisis and one of myeloid blast crisis, leukemia cells had high 5'-N activity, while there was a little or no detectable activity in those from four cases of myeloid blast crisis and all of CML in chronic phase. ADA activity was high in seven of nine patients with blast crisis. Taken together, leukemia cells from two cases of lymphoid blast crisis had high ADA and 5'-N activities comparable to those in acute lymphocytic leukemia (ALL) cells. In contrast, the enzyme activities of leukemia cells from all but one patient in myeloid blast crisis were in a range similar to acute myeloid leukemia cells. The implications of these findings are as follows: (1) 5'-N may be used as a new biochemical marker of CML in lymphoid blast crisis. (2) Some lymphoid cells of CML in blast crisis have high ADA, 5'-N, and TdT activities and thus are very similar to ALL cells.     

Characterization of Thy-1 (CDw90) expression in CD34+ acute leukemia

Thy-1 (CDw90) is a phosphatidylinositol-anchored cell surface molecule which, when coexpressed with CD34 in normal human bone marrow, identifies a population of immature cells that includes putative hematopoietic stem cells. To date, the characterization of Thy-1 expression has been confined largely to normal tissues and cell lines. In this study, we evaluated the frequency and intensity of Thy-1 expression as defined by reactivity with the anti-Thy-1 antibody 5E10 in 38 cases of CD34+ acute leukemia (21 acute myelogenous leukemia [AML], 8 chronic myelogenous leukemia [CML] in blast crisis, and 9 acute lymphoblastic leukemia [ALL]). In 34 of 38 cases (89%) the CD34+ cells lacked expression of the Thy-1 antigen. High-density Thy-1 expression was found in 1 case of CML in lymphoid blast crisis, and low- density Thy-1 expression was identified on a portion of the leukemic cells in 2 cases of AML with myelodysplastic features, and 1 case of CML in myeloid blast crisis, suggesting a possible correlation between Thy-1 expression and certain instances of stem cell disorders such as CML and AML with dysplastic features. In contrast, the dissociation of Thy-1 and CD34 expression in the majority of acute leukemias studied suggests that the development of these leukemias occurs at a later stage than the hematopoietic stem cell. Characterization of Thy-1 expression in acute leukemia may eventually provide insights into the origin of the disease. In addition, separation of leukemic blasts from normal stem cells based on Thy-1 expression may prove useful in assessing residual disease, as well as in excluding leukemic blasts from stem cell preparations destined for autologous bone marrow or peripheral stem cell transplantation.     

Homozygous deletions of the p16 tumor-suppressor gene are associated with lymphoid transformation of chronic myeloid leukemia

The p16 gene, also referred to as MTS1, INK4, CDK4I, or CDKN2, at chromosome 9p21 has recently been described as a tumor suppressor that may be involved in a wide range of tumors. We have used a semiquantitative multiplex polymerase chain reaction assay to search for deletions of the p16 gene in 34 patients with chronic myeloid leukemia in blast crisis (CML BC), 19 patients with acute lymphoblastic leukemia (ALL), and 25 patients with acute myeloid leukemia (AML). Homozygous deletions of p16 exons were found in 5 of 10 (50%) patients with CML in lymphoid BC and in 5 (26%) ALL patients, but in only 1 (2%) case with AML. No deletions were found in CML BC of nonlymphoid phenotype. Comparison of chronic phase DNA or remission DNA with acute leukemia DNA in 5 individuals showed that the p16 deletions were acquired and not inherited, directly implicating these lesions in the pathogenesis of the disease. We conclude that functional elimination of the p16 gene, or a closely mapping gene, is involved in a significant number of patients with CML in lymphoid transformation.     

Propagation of human blastic myeloid leukemias in the SCID mouse.

Existing in vitro culture technology does not permit the routine propagation of most human myeloid leukemias. Previous work has shown the usefulness of mice with severe combined immunodeficiency (SCID) for the growth of human lymphoblastic leukemia. We show here that human myeloid cell lines and bone marrow samples from patients with acute myeloid leukemia (AML) and blast crisis of chronic myeloid leukemia (CML) also grow in SCID mice. Human AML or CML cell lines (three of three lines tested) grew in the bone marrow and peripheral blood of the mice after intravenous (IV) inoculation in a pattern closely resembling human AML. To define the best conditions for the growth of primary human myeloid leukemia cells, samples were transplanted into mice at several alternative sites. Using flow cytometry and Southern analysis, mice were analyzed at defined intervals up to 36 weeks after transplantation for the presence of human cells in various tissues. For four of four patients with AML and two of two patients with blast crisis of CML, myeloblasts grew locally at the site of implantation and were detected in the murine hematopoietic tissues. In contrast, marrow implants from patients in the chronic phase of CML (six patients) showed infrequent and limited myeloid growth in the mice. These findings demonstrate that the SCID mouse is a reproducible system for the propagation of blastic human myeloid leukemias. The differential growth of early- versus late-phase CML suggests that the SCID mouse may be a useful assay for identifying biologically aggressive leukemias early in their clinical presentation.     

Acute lymphoblastic leukemia without the Philadelphia chromosome occurring in chronic myelogenous leukemia with the Philadelphia chromosome

The blast crisis in chronic myelogenous leukemia (CML) is related to the evolution of a Philadelphia chromosome (Ph)-positive clone. Secondary chromosomal abnormalities accompanied by t(9;22) are found in 70-80% of blast crises. Here we describe a patient with Ph-positive CML, who developed Ph-negative acute lymphoblastic leukemia (ALL). A 52-year-old man was diagnosed with CML with the Ph chromosome in the chronic phase. He achieved a partial cytogenetic response after 4 months of imatinib mesylate therapy. After 8 months, common ALL occurred. At that time his karyotype was normal and the Ph chromosome was not noted.     

Cell lineage heterogeneity in blast crisis of chronic myeloid leukaemia

Blast cells from 45 patients with chronic myeloid leukaemia in blast crisis (CML-BC) were immunologically phenotyped with a panel of 26 monoclonal antibodies and studied for terminal deoxynucleotidyl transferase (TdT) content. Out of 45 blast-populations, 28 showed a myeloid, 14 a lymphoid, two a mixed and one an unclassifiable marker profile. In contrast to acute myeloid leukaemia (AML), we found frequent involvement of the thrombopoietic and erythropoietic systems in myeloid CML-BC. Furthermore, the marker profile on blast cells in myeloid CML-BC was different from that seen in AML. The blast cells in lymphoid blast crises of CML displayed the same lymphoid marker profile as those in acute lymphoblastic leukaemia. In three of 16 patients who were serially tested, we observed phenotypic changes in the blast cell populations. In one patient the blasts changed from lymphoid to myeloid type while remaining TdT-positive; in another case the blasts switched from granulomonocytic TdT-negative to granulomonocytic TdT-positive. In the third patient erythroid precursor cells appeared as the disease progressed. The results indicate the capacity of blast populations in CML-patients during blast crisis to differentiate along several pathways.     

Liposomal daunorubicin,fludarabine, and cytarabine (FLAD) as bridge therapy to stem cell transplant in relapsed and refractory acute leukemia

Therapeutic options for patients with relapsed or refractory acute leukemia are still undefined and often unsatisfactory. We report the outcome of 79 patients with relapsed-refractory acute leukemia treated with fludarabine, cytarabine, and liposomal daunorubicin (FLAD regimen) followed by hematopoietic stem cell transplantation (HSCT), when clinically indicated, between May 2000 and January 2013. Forty-one patients had acute myeloid leukemia (AML), and 38 had acute lymphoblastic leukemia (ALL). Two patients with myeloid blast crises of CML and three with lymphoid blast crises were included in the AML and ALL subgroups, respectively. Median age was 48 years (range 13–77). FLAD was well tolerated with negligible, nonhematological toxicity. Six patients (7.5 %) died before response evaluation. Forty-seven patients achieved hematologic complete response (CR). Complete remission rate was 53 and 65 % among AML and ALL patients, respectively. No CR was recorded among 11 refractory AML patients. Twenty-four patients (30 %) underwent HSCT. Nine patients received stem cells from an HLA identical sibling, and 15 from an alternative donor (3 unrelated matched, 12 haploidentical sibling). Median overall survival in AML and ALL patients receiving FLAD therapy was 9 and 8 months, respectively. A 5-year projected OS for patients receiving the whole program (FLAD + HSCT) was 24 % for AML patients (median survival 43 months), 28 % for ALL patients treated in relapse (median survival 15 months), and 0 % for ALL patients treated for refractory disease. In this paper, we show that FLAD seems to be an effective bridge therapy to HSCT for a part of poor prognosis acute leukemia patients. However, prospective studies are needed to confirm our results.     

Clinical impact of graft-versus-host disease against leukemias not in remission at the time of allogeneic hematopoietic stem cell transplantation from related donors. The Japan Society for Hematopoietic Cell Transplantation Working Party

Acute graft-versus-host disease (GVHD) increases post-transplant mortality and morbidity, but exerts a potent graft-versus-leukemia (GVL) effect. To clarify the impact of GVHD on outcome after transplant in aggressive diseases, patients with acute myeloid or lymphoblastic leukemia (AML, n = 366 or ALL, n = 255) in nonremission states, or chronic myelogenous leukemia (CML, n = 180) in accelerated phase (AP) or blastic crisis (BC), who received allogeneic hematopoietic stem cell transplantation (HSCT) from a related donor between 1991 and 2000, were analyzed. Significant improvement in overall and disease-free survival (DFS) was detected with grade I acute GVHD in AML (P = 0.0002 for overall survival and 0.0009 for DFS, respectively) and in CML (P = 0.0256 and 0.0366, respectively), while the trend towards improved survival was observed in ALL. Relapse rate was lower in grade I acute GVHD than in grade II in all three diseases, suggesting that treatment for grade II GVHD may compromise the GVL effect associated with GVHD. Chronic GVHD was found to suppress relapse in CML and ALL, but not in AML, although no improvement in survival was observed in any disease category. Our results suggest that treatment for grade II acute GVHD may need to be attenuated in transplant for refractory leukemias.     

Immunophenotyping of acute myeloid leukemia using monoclonal antibodies and the alkaline phosphatase-antialkaline phosphatase technique

The leukemic cells from 41 cases of acute myeloid leukemia (AML) and 17 cases of acute lymphocytic leukemia (ALL) were immunophenotyped by the alkaline phosphatase-antialkaline phosphatase (APAAP) immunocytochemical technique utilizing eight monoclonal antibodies (MoAb) reactive with cells of myeloid origin and seven MoAb reactive with lymphoid antigens. Ninety percent of the cases of AML reacted with one or more of the pan-myeloid MoAb, My7, My9, or 20.3. Reactivity of the myeloid panel of MoAb showed some correlation with the French-American-British (FAB) classification of AML. Five of six cases of acute promyelocytic leukemia (APL) were HLA-DR negative; the one HLA-DR-positive APL had a minor population of HLA-DR-negative promyelocytes. OKM5 and/or My4 reacted with 16 of 16 monocytic leukemias. No specific marker of early erythroid development was identified. AP3, a MoAb reactive with platelet glycoprotein (GPIIIa), was specific for acute megakaryoblastic leukemia. Immunocytochemistry was also helpful in classifying seven cases of AML with equivocal or negative routine cytochemistry. Two cases of AML had minor populations of blasts detected by the APAAP technique that were immunologically distinct from the major blast population; these minor populations emerged as the predominant cell type at relapse. Two cases of ALL expressed multiple myeloid and lymphoid antigens. Two other cases that morphologically were ALL reacted with only myeloid MoAb; one consisted entirely of immature basophils on ultrastructural examination. Immunophenotyping results using the APAAP technique were comparable with those obtained with flow cytometry. The APAAP technique is a reliable method for immunophenotyping leukemia that complements other methods of immunologic evaluation. The primary advantages of this method include its use with routinely prepared blood and bone marrow smears and the ability to correlate immunocytochemical reactions with morphology.     

High incidence of biallelic point mutations in the Runt domain of the AML1/PEBP2 alpha B gene in Mo acute myeloid leukemia and in myeloid malignancies with acquired trisomy 21

The AML1 gene, situated in 21q22, is often rearranged in acute leukemias through t(8;21) translocation, t(12;21) translocation, or less often t(3;21) translocation. Recently, point mutations in the Runt domain of the AML1 gene have also been reported in leukemia patients. Observations for mutations of the Runt domain of the AML1 gene in bone marrow cells were made in 300 patients, including 131 with acute myeloid leukemia (AML), 94 with myelodysplastic syndrome (MDS), 28 with blast crisis chronic myeloid leukemia (CML), 3 with atypical CML, 41 with acute lymphoblastic leukemia (ALL), and 3 with essential thrombocythemia (ET). Forty-one of the patients had chromosome 21 abnormalities, including t(8;21) in 6 of the patients with AML, t(12;21) in 8 patients with ALL, acquired trisomy 21 in 17 patients, tetrasomy 21 in 7 patients, and constitutional trisomy 21 (Down syndrome) in 3 patients. A point mutation was found in 14 cases (4.7%), including 9 (22%) of the 41 patients with AML of the Mo type (MoAML) (none of them had detectable chromosome 21 rearrangement) and 5 (38%) of the 13 myeloid malignancies with acquired trisomy 21 (1 M1AML, 2 M2AML, 1 ET, and 1 atypical CML). In at least 8 of 9 mutated cases of MoAML, both AML alleles were mutated: 3 patients had different stop codon mutations of the 2 AML1 alleles, and 5 patients had the same missense or stop codon mutation in both AML1 alleles, which resulted in at least 3 of the patients having duplication of the mutated allele and deletion of the normal residual allele, as shown by FISH analysis and by comparing microsatellite analyses of several chromosome 21 markers on diagnosis and remission samples. In the remaining mutated cases, with acquired trisomy 21, a missense mutation of AML1, which involved 2 of the 3 copies of the AML1 gene, was found. Four of the 7 mutated cases could be reanalyzed in complete remission, and no AML1 mutation was found, showing that mutations were acquired in the leukemic clone. In conclusion, these findings confirm the possibility of mutations of the Runt domain of the AML1 gene in leukemias, mainly in MoAML and in myeloid malignancies with acquired trisomy 21. AML1 mutations, in MoAML, involved both alleles and probably lead to nonfunctional AML1 protein. As AML1 protein regulates the expression of the myeloperoxidase gene, the relationship between AML1 mutations and Mo phenotype in AML will have to be further explored. (Blood. 2000;96:2862-2869)     

RNAi screening of the kinome with cytarabine in leukemias

To identify rational therapeutic combinations with cytarabine (Ara-C), we developed a high-throughput, small-interference RNA (siRNA) platform for myeloid leukemia cells. Of 572 kinases individually silenced in combination with Ara-C, silencing of 10 (1.7%) and 8 (1.4%) kinases strongly increased Ara-C activity in TF-1 and THP-1 cells, respectively. The strongest molecular concepts emerged around kinases involved in cell-cycle checkpoints and DNA-damage repair. In confirmatory siRNA assays, inhibition of WEE1 resulted in more potent and universal sensitization across myeloid cell lines than siRNA inhibition of PKMYT1, CHEK1, or ATR. Treatment of 8 acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic myeloid leukemia (CML) cell lines with commercial and the first-in-class clinical WEE1 kinase inhibitor MK1775 confirmed sensitization to Ara-C up to 97-fold. Ex vivo, adding MK1775 substantially reduced viability in 13 of 14 AML, CML, and myelodysplastic syndrome patient samples compared with Ara-C alone. Maximum sensitization occurred at lower to moderate concentrations of both drugs. Induction of apoptosis was increased using a combination of Ara-C and MK1775 compared with using either drug alone. WEE1 is expressed in primary AML, ALL, and CML specimens. Data from this first siRNA-kinome sensitizer screen suggests that inhibiting WEE1 in combination with Ara-C is a rational combination for the treatment of myeloid and lymphoid leukemias.     

Paraplegia as the presenting manifestation of extramedullary megakaryoblastic transformation of previously undiagnosed chronic myelogenous leukemia

Extramedullary tumors, also known as granulocytic sarcomas (GS), occur most frequently in acute myelogenous leukemia (AML). They may signal the onset of the accelerated phase of chronic myelogenous leukemia (CML) or the blastic transformation of a myeloproliferative disorder. Occasionally, a GS may be the presenting sign of undiagnosed AML, and rarely the presenting sign of undiagnosed CML or aleukemic leukemia. Paraplegia due to a spinal cord GS is an extremely rare presentation of undiagnosed leukemia. This is the first case report of paraplegia as the presenting manifestation of extramedullary megakaryoblastic transformation of previously undiagnosed CML. A 53-year-old woman reported back pain for 6 days, rapidly progressing to paraplegia. Physical examination noted a large abdominal mass and flaccid paralysis in both lower extremities. Spinal MRI revealed a T4-T6 vertebral mass causing spinal stenosis and cord compression. Tumor debulking and laminectomy were performed emergently. The tumor consisted of noncohesive blast cells. The CBC revealed a leukocyte count of 238,300/microl and a differential consistent with CML. Reexamination of the patient found that the abdominal mass was a giant spleen. Further immunohistochemical studies of the tumor were consistent with extramedullary acute megakaryoblastic blast transformation of CML. Although extramedullary blast crises herald the accelerated phases in approximately 10% of CML cases, megakaryoblastic blast transformation of CML accounts for less than 3% of these cases. The combination of acute paraplegia and megakaryoblastic transformation in a previously undiagnosed patient with CML is extremely rare and may pose a diagnostic dilemma.     

Acute lymphoblastic leukemia with myeloperoxidase activity

The French-American-British (FAB) classification of acute leukemias is based on the light microscopic detection of myeloperoxidase (MPO) activity in blast cells. Cells with MPO activity in >3% of cells are classified as acute myeloid leukemia (AML) and usually express myeloid cell surface antigens. We describe a case of acute leukemia in which the blast cells have lymphoid morphology, ultrastructure, immunophenotype, and molecular rearrangements, but express significant amounts of MPO. We discuss the incidence, features, and outcome of MPO-positive acute lymphoblastic leukemia (ALL). © 1996 Wiley-Liss, Inc.     

Philadelphia-positive T-cell acute lymphoblastic leukemia with polymyositis, migratory polyarthritis and hypercalcemia following a chronic myeloid leukemia

Transformation of chronic myeloid leukemia (CML) often results in acute myeloblastic or, less frequently, in precursor B-cell acute lymphoblastic leukemia (ALL). T-cell blast crisis is rare. Hypercalcemia has also been described as a rare complication of CML, but this usually occurs as a terminal event. Here we report a case of a 35-year-old woman who developed a CD4(+)/CD8(+) T-cell ALL 2 years after the diagnosis of a typical Ph(+) CML. Polymyositis and polyarthritis preceded by 4 months, and symptomatic hypercalcemia occurred just before blastic transformation, probably representing paraneoplastic manifestations of the disease.