Mixed Phenotypic Acute Leukemia Presenting as Mediastinal Mass-2 Cases

Mixed phenotype acute leukemia symbolizes a very small subset of acute leukemia that simply cannot be allocated as lymphoid or myeloid lineage. The 2008 World Health Organisation classification established stringent standard for diagnosis of mixed phenotype acute leukemia, accentuating myeloperoxidase for myeloid lineage, cytoplasmic CD3 for T lineage and CD19 with other B markers for B lineage obligation. Mixed phenotype leukemia is rare and 3–5 % of acute leukmias of all age groups, is associated with poor outcome with overall survival of 18 months. We wish to present two cases of mixed phenotypic acute leukemia who presented with mediastinal masses, were suspected to be T cell lymphoma/leukemia clinically and radiologically. In one case, tissue diagnosis was given as lymphoma for which treatment was given. These cases show that patients diagnosed as lymphoma on histopathology can be cases of mixed phenotype acute leukemia and varying specific treatment protocols and follow up are required. Awareness of these entities will help in proper diagnosis and treatment.     

Prognosis of children with mixed phenotype acute leukemia treated on the basis of consistent immunophenotypic criteria

Background

Mixed phenotype acute leukemia (MPAL) represents a diagnostic and therapeutic dilemma. The European Group for the Immunological Classification of Leukemias (EGIL) scoring system unambiguously defines MPAL expressing aberrant lineage markers. Discussions surrounding it have focused on scoring details, and information is limited regarding its biological, clinical and prognostic significance. The recent World Health Organization classification is simpler and could replace the EGIL scoring system after transformation into unambiguous guidelines.

Design and Methods

Simple immunophenotypic criteria were used to classify all cases of childhood acute leukemia in order to provide therapy directed against acute lymphoblastic leukemia or acute myeloid leukemia. Prognosis, genotype and immunoglobulin/T-cell receptor gene rearrangement status were analyzed.

Results

The incidences of MPAL were 28/582 and 4/107 for children treated with acute lymphoblastic leukemia and acute myeloid leukemia regimens, respectively. In immunophenotypic principal component analysis, MPAL treated as T-cell acute lymphoblastic leukemia clustered between cases of non-mixed T-cell acute lymphoblastic leukemia and acute myeloid leukemia, while other MPAL cases were included in the respective non-mixed B-cell progenitor acute lymphoblastic leukemia or acute myeloid leukemia clusters. Analogously, immunoglobulin/T-cell receptor gene rearrangements followed the expected pattern in patients treated as having acute myeloid leukemia (non-rearranged, 4/4) or as having B-cell progenitor acute lymphoblastic leukemia (rearranged, 20/20), but were missing in 3/5 analyzed cases of MPAL treated as having T-cell acute lymphobastic leukemia. In patients who received acute lymphoblastic leukemia treatment, the 5-year event-free survival of the MPAL cases was worse than that of the non-mixed cases (53±10% and 76±2% at 5 years, respectively, P=0.0075), with a more pronounced difference among B lineage cases. The small numbers of MPAL cases treated as T-cell acute lymphoblastic leukemia or as acute myeloid leukemia hampered separate statistics. We compared prognosis of all subsets with the prognosis of previously published cohorts.

Conclusions

Simple immunophenotypic criteria are useful for therapy decisions in MPAL. In B lineage leukemia, MPAL confers poorer prognosis. However, our data do not justify a preferential use of current acute myeloid leukemia-based therapy in MPAL.     

Mixed phenotype acute leukemia of T/myeloid type with a prominent cellular heterogeneity and unique karyotypic aberration 45,XY, dic(11;17)

Introduction. A 26‐yr‐old male patient with mixed phenotype acute leukemia of T/myeloid type with prominent leukemic cell heterogeneity, and the presence of a so far unreported karyotype aberration in this type of acute leukemia 45,XY, dic(11;17)(11qter→11p11.2::17p11.2→17qter) is presented. Methods. Flow immunocytometry was performed by direct multicolor immunofluorescent technique on bone marrow aspirates. Cytogenetic analyses were performed using G‐banding method by direct preparation of unstimulated bone marrow cells and following 24 hours of culture in RPMI 1540 culture medium with 25% fetal calf serum at 37°C Results. The flow immunocytometry of bone marrow nucleated cells revealed the existance of three distinct blast cell populations with overlapping immunophenotypes. Predominant blast cell population had an early myeloid phenotype and aberrant expression of CD7 antigen (HLA‐DR⁺, CD34⁺, anti‐MPO⁺, CD117⁺, CD33⁺, CD13⁺, CD7^+low, cyCD3^?, TdT^?). The other two blast cell populations, smaller in cell diameter and less sizable in cell proportion, both shared the T‐lymphoid features. The patient was treated with ADE protocol (etoposide, cytarabine and doxorubicine). A complete remission was achieved and lasted 5 months. Conclusion. A case of MPAL with complex biological features, 45,XY, dic(11;17)(11qter→11p11.2::17p11.2→17qter) karyotype and an aggressive, therapy‐resistant clinical course, is presented.     

Redefining the biological basis of lineage-ambiguous leukemia through genomics: BCL11B deregulation in acute leukemias of ambiguous lineage

Acute leukemias of ambiguous lineage (ALAL), including mixed phenotype acute leukemia (MPAL) and related entities such as early T-cell precursor acute leukemia (ETP-ALL), remain diagnostic and clinical challenges due to limited understanding of pathogenesis, reliance of immunophenotyping to classify disease, and the lack of a rational approach to guide selection of appropriate therapy. Recent studies utilizing genomic sequencing and complementary approaches have provided key insights that are changing the way in which such leukemias are classified, and potentially, treated. Several recurrent genomic alterations define leukemias that straddle immunophenotypic entities, such as ZNF384-rearranged childhood B-ALL and B/myeloid MPAL, and BCL11B-rearranged T/myeloid MPAL, ETP-ALL and AML. In contrast, some cases of MPAL represent canonical ALL/AML entities exhibiting lineage aberrancy. For many cases of ALAL, experimental approaches indicate lineage aberrancy arises from acquisition of a founding genetic alteration into a hematopoietic stem or progenitor cell. Determination of optimal therapeutic approach requires genomic characterization of uniformly treated ALAL patients in prospective studies, but several approaches, including kinase inhibitors and BH3 mimetics may be efficacious in subsets of ALAL.     

Children Diagnosed as Mixed-Phenotype Acute Leukemia Didn’t Benefit from the CCLG-2008 Protocol,Retrospective Analysis from Single Center

Mixed phenotype acute leukemia (MPAL) is a rare type of acute leukemia with a poor clinical outcome which lacks specific therapy. To evaluate the therapeutic efficiency of CCLG-2008 protocol used for acute lymphoblastic leukemia (ALL) in China on MPAL children who were initially diagnosed as ALL by morphology, we reviewed patients’ database diagnosed as ALL and MPAL according to WHO classification and compared their outcomes from July 2008 to June 2012. Total newly enrolled ALL in this study were 309 cases by morphology, in which ten cases were identified as MPAL mainly by immunophenotyping: B+ myeloid (3/10), T+ myeloid (2/10), B + T (4/10), trilineage (1/10). Two cases were classified as intermediate risk (IR) and 8 cases were high risk (HR) according to the CCLG-2008 criteria. Only one case of IR survived and others died due to primary resistance of chemotherapy and relapse. Compared with MPAL, ALL children in IR and HR had a longer survival (28.1 vs 9.5 months, p < 0.0001) and lower relapse (16.3 vs 85.7 %, p = 0.0002). In a summary, our result indicated that MPAL in children is a poor-risk disease which needs personalized therapy to improve outcome.

Electronic supplementary material

The online version of this article (doi:10.1007/s12288-014-0372-6) contains supplementary material, which is available to authorized users.     

Clinical and biological characteristics of adult biphenotypic acute leukemia in comparison with that of acute myeloid leukemia and acute lymphoblastic leukemia: a case series of a Chinese population

Background

Biphenotypic acute leukemia is a rare disorder that is difficult to diagnose. It displays features of both myeloid and lymphoid lineage. There is still a lack of studies in biphenotypic acute leukemia in a Chinese population. We present here a comprehensive investigation of the clinical and biological characteristics, and outcome of biphenotypic acute leukemia in our hospital in over a seven year period.

Design and Methods

We retrospectively analyzed 452 adult acute leukemia patients diagnosed according to French-American-British (FAB) classification and biphenotypic acute leukemia diagnosed according to European Group for the Immunological Characterization of Leukemias (EGIL) classification, respectively. Biological characteristics, response to treatment, and outcome were examined in biphenotypic acute leukemia patients and compared with that in acute myeloid leukemia and acute lymphoblastic leukemia patients with complete follow-up profiles diagnosed in the same period.

Results

Of 452 acute leukemia patients, 21 cases (4.6%) were diagnosed as biphenotypic acute leukemia. Among them, 14 (66.7%) were B lymphoid and myeloid, 5 (23.8%) were T lymphoid and myeloid, one (4.8%) was T/B lymphoid and one (4.8%) was trilineage differentiation. When compared with acute myeloid leukemia and acute lymphoblastic leukemia, patients with biphenotypic acute leukemia showed significantly higher incidence of CD34 antigen expression, unfavorable karyotypes, and extramedullary infiltration (p<0.05). In this cohort of patients with biphenotypic acute leukemia, t(9;22) was the most common abnormality in chromosome structure. The median disease-free survival and overall survival in biphenotypic acute leukemia patients was five months and ten months, respectively, significantly shorter than those in acute myeloid leukemia and acute lymphoblastic leukemia patients (p<0.05).

Conclusions

The prognosis of biphenotypic acute leukemia patients is poor when compared with de novo acute myeloid leukemia or acute lymphoblastic leukemia. Biphenotypic acute leukemia patients showed a much higher incidence of CD34 antigen expression, complex abnormal karyotype, extramedullary infiltration, relapse, and resistance to therapy after relapse.     

Successful treatment of Philadelphia chromosome-positive mixed phenotype acute leukemia by appropriate alternation of second-generation tyrosine kinase inhibitors according to BCR-ABL1 mutation status

Philadelphia chromosome-positive mixed phenotype acute leukemia (Ph⁺MPAL) is a rare type of acute leukemia having myeloid and lymphoid features. In the present study, we describe the successful treatment of a 71-year-old Japanese female patient with Ph⁺MPAL by the alternation of second-generation tyrosine kinase inhibitors according to BCR-ABL1 mutations. The patient survived in her third complete remission (CR) for over 4 years. In her first CR, the patient was treated with multiple-agent chemotherapy and underwent maintenance therapy with imatinib and monthly vincristine and prednisolone (VP). At the first relapse, an examination of the bone marrow revealed a transformation into acute lymphoblastic leukemia and an F317L mutation in BCR-ABL1 gene, which responded preferentially to nilotinib over dasatinib. She achieved second CR, and nilotinib with VP therapy was selected for maintenance treatment. At second relapse, BCR-ABL1 mutational analysis revealed Y253H mutation instead of F317L mutation, resulting in resistance to nilotinib. The patient achieved third CR with dasatinib and VP therapy, and maintained CR with this treatment. This suggests that appropriate alternation of TKIs may contribute to long-term survival in elderly patients with Ph⁺MPAL.     

Diagnosing and treating mixed phenotype acute leukemia: a multicenter 10-year experience in México

Mixed phenotype acute leukemia (MPAL) in adults represents nearly 2 to 5 % of all acute leukemia cases. There are two large studies throughout the world and only case reports and small series have been reported in Latin America. This study retrospectively analyses the clinical characteristics and survival of 27 patients with MPAL evaluated in three medical institutions of Mexico. All cases meet World Health Organization 2008 criteria; 70.3 % of patients had B lymphoid/myeloid lineage MPAL. Induction chemotherapy protocols included 7?+?3 hyper-CVAD, high-density schedules, and pediatric-like regimens such as New York II and total XI. Complete remission was achieved in 23/27 patients (85.2 %). Only one patient died due to chemotherapy-induced aplasia during remission induction (5.2 %). In 68 % of cases, we were able to administer maintenance therapy as a regimen in lymphoblastic leukemia. At the time of analysis, 70.4 % of the patients in the entire cohort had died mainly as result of disease progression (73.6 %). Disease-free survival was 13 months (95 % CI, 9.6–16.3 months) and overall survival was 14.8 months (95 % CI 13.4–16.27). Survival rates are low and standardized therapy for the management of this type of leukemia is still lacking. This is the largest series reported in Mexico and to the best of our knowledge in Latin America.     

Myeloid/natural killer cell precursor blast crisis of chronic myelogenous leukemia with two Philadelphia (Ph-1) chromosomes

We report on a 30-year-old patient with blast crisis of a chronic myelogenous leukemia (CML) that shows immunophenotypic features similar to those of the myeloid/natural killer (NK) cell precursor leukemia previously described. Expression of CD13/CD33/CD65 as well as MPO+/LF- blasts was classified as a myelogenous blast crisis of a CML. In addition, the blasts were positive for CD7/CD56. Other lymphoid markers were not expressed. Cytogenetic and molecular cytogenetic examinations showed two Philadelphia (Ph-1) chromosomes and a trisomy 8. Similar to expression of the myeloid/NK cell precursor phenotype in acute myelogenous leukemia (AML), it is possible to exhibit this phenotype in Ph-1-positive CML. Only one case report of myeloid/NK precursor phenotype blast crisis of CML was found in the literature. Therefore, it is not clear whether this phenotype is a distinct biologic and clinical disease entity of CML, as is the case in the respective AML phenotype.     

交叉表达淋系和髓系相关抗原的急性白血病的生物学及临床特征研究

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

Features and clinical outcomes in 40 patients with mixed-lineage acute leukemia in a single center

Abstract

Mixed-lineage acute leukemia (MAL) is characterized as acute leukemia involving acute myeloid cells and lymphoid cells at the same time. It is easily misdiagnosed because of the dual characteristics involving both lymphoid and myeloid cells and has a poor prognosis. We retrospectively analyzed the features and treatment effectiveness in a single center in 40 patients with MAL. The morphology was consistent with acute lymphoblastic leukemia (ALL) (47.5%) or acute myeloid leukemia (AML) (20%) or was inconclusive (32.5%). Twenty-two patients were characterized as B/myeloid, and 18 patients as T/myeloid. Cytogenetics showed t(9;22)/(Ph⁺) (12.5%) and 11q23/MLL rearrangements (6.25%). The rate of first complete remission for patients undergoing chemotherapy based on the features of both ALL and AML and of either ALL or AML was 71.4 and 42.9%, respectively. The 1-year overall survival rates were 37.5 and 60.0% for chemotherapy and chemotherapy followed by haploidentical hematopoietic stem cell transplantation (HSCT), respectively. The 1-year disease-free survival rates were 25.0 and 50.0% for chemotherapy and chemotherapy followed by HSCT, respectively. These results showed that MAL is confirmed to be a poor-risk disease. The chemotherapy for remission induction should be based on both myeloid cells and lymphoid cells. Transplantation should be performed after the first remission.     

CD7+, CD4-, CD8- acute leukemia: a syndrome of malignant pluripotent lymphohematopoietic cells

Following our initial observation of in vivo conversion of CD7+, CD4-, CD8- acute lymphoblastic leukemia (ALL) cells from lymphoid to myeloid lineages (Proc Natl Acad Sci (USA) 81:253, 1984) we have studied eight additional cases of ALL with this leukemic cell phenotype. The CD7+, CD4-, CD8- phenotype was associated with a distinct clinical entity with those affected predominantly male (either less than 35 years or greater than 65 years of age), with frequent mediastinal and/or thymic masses, skin and CNS disease, high peripheral WBC counts, and bone marrow blasts that were morphologically L1 or not ascribable to a specific lineage. These patients did not respond to conventional chemotherapeutic regimens for either acute lymphoid or myeloid leukemias. No common karyotype or T-cell gene rearrangement pattern could be defined. Importantly, seven of eight patient's leukemic cells studied were capable of multilineage (myeloid, erythroid, monocytoid, megakaryocytoid, and lymphoid) differentiation in vitro. Data is presented suggesting that CD7+, CD4-, CD8- leukemias, in many instances, are leukemias of immature hematopoietic cells. The development of novel therapeutic approaches to this form of leukemia will be necessary to alter its poor prognosis.     

Allogeneic hematopoietic stem cell transplantation for adult patients with mixed phenotype acute leukemia: results of a matched‐pair analysis

Adult patients with mixed phenotype acute leukemia (MPAL) have a poor prognosis, and the therapeutic role of allogeneic stem cell transplantation (allo‐SCT) for MPAL remains to be elucidated. Thus, we retrospectively assessed the efficacy of allo‐SCT for MPAL. Eighteen patients with MPAL were identified from the transplant outcome database of Kanto Study Group for Cell Therapy (KSGCT). We also selected 215 patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) as control cohorts using an optimal matching method. The 5‐yr overall survival (OS) rate of patients with MPAL was 48.1%, and patients in remission at the time of transplant showed significantly better survival than those not in remission (5‐yr OS: 71.8% vs. 0%, P = 0.001). No significant differences were seen in OS when stratifying patients according to immunophenotype, cytogenetic abnormalities, or the type of induction therapy. The 5‐yr OS rate of patients with MPAL was not significantly different compared with AML control patients (48.1% vs. 48.1%; P = 0.855) or ALL control patients (48.1% vs. 37.8%; P = 0.426). These results suggested that allo‐SCT is an effective treatment for MPAL, especially early in the disease course, and innovative transplant approaches are warranted to improve the transplant outcome of patients with MPAL who are not in remission.     

对过继免疫治疗中外周血单个核细胞采集术的探讨

目的观察细胞表面分化抗原CD117在急性髓细胞白血病(AML)与急性淋巴细胞白血病(ALL)的表达差异及其意义,评价其作为髓系抗原的特异性。方法采用CD45/SSC双参数散点图设门法进行三色流式细胞术分析。直接免疫荧光标记法标记20种细胞表面分化抗原,经流式细胞仪测定,对286例白血病患者骨髓或外周血白血病细胞CD117及其他表面抗原的表达结果进行分析。结果CD117在ALL中表达率极低,仅占2%,在AML中表达率为56.9%,2者差异有统计学意义(P<0.05)。在AML各型中,CD117在M3亚型中的表达率最低,为23.1%。本组数据统计结果显示CD117的髓系特异度为0.98(SE=0.014),髓系敏感度为0.57(SE=0.04),统计结果表明CD117比CD13、CD33更具髓系特异性(P<0.05)。结论与CD13和CD33相比较,CD117在作为髓系标记的敏感度不如前两者高,但它更具有髓系特异度,因而可作为排除ALL及辅助诊断AML的标志。     

Acute myeloid/T‐lymphoblastic leukaemia (AMTL): a distinct category of acute leukaemias with common pathogenesis in need of improved therapy

Advances in the classification of acute leukaemias have led to improved outcomes for a substantial fraction of patients. However, chemotherapy resistance remains a major problem for specific subsets of acute leukaemias. Here, we propose that a molecularly distinct subtype of acute leukaemia with shared myeloid and T cell lymphoblastic features, which we term acute myeloid/T‐lymphoblastic leukaemia (AMTL), is divided across 3 diagnostic categories owing to variable expression of markers deemed to be defining of myeloid and T‐lymphoid lineages, such as myeloperoxidase and CD3. This proposed diagnostic group is supported by (i) retained myeloid differentiation potential during early T cell lymphoid development, (ii) recognition that some cases of acute myeloid leukaemia (AML) harbour hallmarks of T cell development, such as T‐cell receptor gene rearrangements and (iii) common gene mutations in subsets of AML and T cell acute lymphoblastic leukaemia (T‐ALL), including WT1, PHF6, RUNX1 and BCL11B. This proposed diagnostic entity overlaps with early T cell precursor (ETP) T‐ALL and T cell/myeloid mixed phenotype acute leukaemias (MPALs), and also includes a subset of leukaemias currently classified as AML with features of T‐lymphoblastic development. The proposed classification of AMTL as a distinct entity would enable more precise prospective diagnosis and permit the development of improved therapies for patients whose treatment is inadequate with current approaches.     

Philadelphia chromosome‐positive mixed phenotype acute leukemia in the imatinib era

Although the introduction of imatinib dramatically improved the outcomes for patients with Philadelphia chromosome‐positive B‐cell precursor acute lymphoblastic leukemia (Ph+BCP‐ALL), the survival benefit of imatinib has not been assessed in the context of Ph+ mixed phenotype acute leukemia (Ph+MPAL). To clarify this important issue, we studied 42 Ph+ acute leukemia (Ph+AL) patients who received intensive chemotherapy and concurrent administration of imatinib. Of the 42 Ph+AL patients, 13 (31%) patients were categorized as Ph+MPAL (positive for both myeloid and B‐cell lineage), 27 (64%) were categorized as Ph+BCP‐ALL, and two (5%) were categorized as Ph+ acute myeloid leukemia. The complete remission rates after the initial induction therapy were not significantly different when comparing Ph+MPAL and Ph+BCP‐ALL patients (100% vs. 85%, respectively, P = 0.14). Likewise, there were no significant differences in the 5‐yr overall survival (OS) or disease‐free survival (DFS) rates when comparing the MPAL and BCP‐ALL groups (OS: 55% vs. 53%, respectively, P = 0.87, DFS: 46% vs. 42%, respectively, P = 0.94). These findings suggest that concurrent imatinib administration with chemotherapy improved the outcomes of Ph+MPAL patients to the level seen in Ph+BCP‐ALL patients and should, therefore, be considered as the standard therapy for these patients.     

Concomitant chronic lymphocytic leukemia and acute myeloid leukemia with an uncommon immunophenotype

We report a case of simultaneous diagnosis of chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML), in which the use of flow cytometry analysis allowed the demonstration of two different cell populations and the study of both immunophenotyping patterns with a large panel of monoclonal antibodies (MoAbs). CLL cells showed a typical immunophenotype with coexpression of B cell markers with CD5, CD23, CD43, and weak surface immunoglobulin light chain restriction expression, whereas the AML population had a very uncommon phenotype with expression of myeloid markers and CD56 and lack of expression of other natural killer (NK) antigens, CD34 and HLA-DR. After chemotherapeutic treatment of AML with two induction courses, the patient achieved complete remission of the AML with persistence of a CD19/CD5 positive population. After consolidation chemotherapy, this latter population was no longer detectable despite the presence of lymphoid nodules in a bone marrow biopsy. Six months after diagnosis, the patient relapsed with AML and died shortly afterwards. Am. J. Hematol. 56:281–287, 1997. © 1997 Wiley-Liss, Inc.     

Simultaneous occurrence of biphenotypic T cell/myeloid lesions involving t(12;13)(p13;q14) in a pediatric patient

This paper chronicles a 2-year-old girl who presented with acute leukemia/lymphoma syndrome of the T cell immunophenotype. At this time, the cytogenetic analysis of her bone marrow cells showed a reciprocal translocation between the short arm of chromosome 12 and the long arm of chromosome 13, t(12;13)(p13;q14). The immunophenotyping of bone marrow blast cells by flow cytometry revealed a population of cells positive for CD56, CD117, CD45, partial CD33, partial HLA-DR, CD13, CD7, CD2 and CD5. Therefore, a diagnosis of acute leukemia with a mixed T cell/myeloid phenotype was made. The patient had a poor response to classic T cell acute lymphocytic leukemia/lymphoma therapy; thus, her treatment was changed to a myeloid leukemia protocol, which produced a good response. She underwent a successful cord blood transplantation from an unrelated HLA partially matched donor. The coexistence of these two phenotypes prompts questions about the existence of clonal instability, which might influence the choice of therapy. The rarity of the t(12;13)(p13;q14) and the coexistence of T cell/myeloid markers suggest a nonrandom association. To the best of our knowledge, this is the first reported case in which a cell clone bearing a t(12;13)(p13;q14) translocation in a mixed T cell/myeloid lesion was detected.     

Transformation of bilineal hybrid acute leukemia to acute lymphoid leukemia: a case report with serial analyses of cytogenetics and gene rearrangement

A 17-year-old male with bilineal hybrid acute leukemia is described. Two-color flow cytometric analysis of blast surface phenotype revealed that there were two groups of blasts which showed either CD 10+ CD 19+ CD 13- CD 33- or CD 10- CD 19- CD 13+ CD 33+, but not both. He developed a complete remission by treatment with vincristine, prednisolone, adriamycin, and L-asparaginase. After 8 months, however, leukemia relapsed and lymphoid blasts were dominant. Cytogenetic analysis at presentation showed 46,XY,t(3;9)(p21;p22), and at relapse it showed 46,XY,t(1;3;9)(1pter----1q32::3p25----3pter;3 qter----3p21::9p22----9pter; 9qter----9p22::3p21----3p25::1q32----1q ter),t(2;19)(p21;q13). Analysis of the heavy chain joining region at diagnosis showed three hybridizing bands, all rearranged, but at relapse only one rearranged band. Analysis of the constant region for the beta T-cell receptor gene (TCR beta) both at diagnosis and at relapse showed one rearranged and one germline band, suggesting that rearrangement of one allele of TCR beta of not only lymphoid but also myeloid blasts occurred. It is considered that the target cell of lymphoid leukemia cells and that of myeloid leukemia cells at diagnosis were the same, which differentiated to two lineages, and the clone which evolved from lymphoid lineage proliferated at relapse.