Neural cell adhesion molecule (CD56)-positive acute myelogenous leukemia and myelodysplastic and myeloproliferative syndromes

Development and validation of an immunoassay for quantification of NCAM-1 in human plasma

BACKGROUND

Neural Cell Adhesion Molecule 1 (NCAM-1), a multifunctional member of the immunoglobulin superfamily, is expressed on the surface of neurons, glia, skeletal muscle, and natural killer cells. NCAM-1 has been implicated as having a role in cell-cell adhesion, involved in development of the nervous system, and for cells involved in the expansion of T cells and dendritic cells which play an important role in immune surveillance. Sensitive and specific methods to quantify non-surface bound NCAM-1 are not available.

METHOD

A sandwich ligand binding assay was developed for quantification of NCAM-1 in plasma and validated using an electro-chemiluminescent (ECL) technology.

RESULTS

The data presented here demonstrated that the validated method met all prespecified criteria for precision, linearity, and accuracy in the range of 62.5 ng/mL to 4000.0 ng/mL, the range believed to be most relevant for plasma. The bioanalytical validation of the assay established the inter-assay coefficient of variation <8 % for calibration points, <2 % for high quality control (HQC), <8 % for medium quality control (MQC) and <19 % for low quality control (LQC) samples. Purified NCAM-1 spike-recovery experiment in plasma was used to determine assay accuracy; nominal concentrations (%) of NCAM-1 ranged from 91 % to 112 % for high and low spike level, respectively. Assay performance was subsequently evaluated for parallelism, selectivity, interference, and stability.

CONCLUSION

NCAM-1 assay has been developed and validated in human plasma and met all assay validation parameters pre-determined during development. Clinical testing of human plasma samples indicated that NCAM-1 does not seem to be influenced by age and was slightly influenced by gender. NCAM-1 assay has potential to be used as a biomarker assay once the assay is subjected to appropriate clinical assessment and diagnostic thresholds are established.

CD33 expression on natural killer cells is a potential confounder for residual disease detection in acute myeloid leukemia by flow cytometry

Detection of minimal/measurable residual disease (MRD) in acute myeloid leukemia (AML) is important for guiding patient-specific clinical management. Natural killer (NK) cells can express various markers not typically associated with NK lineage, potentially confounding the detection of MRD by flow cytometry. We have observed CD33 expression on NK cells when evaluating for AML MRD in routine clinical practice in multiple patient samples. To characterize CD33 expression on NK cells, 40 peripheral blood or bone marrow samples with NK cells present at >5% of lymphocytes were selected for further assessment of NK cell phenotype and CD33 expression. Seven of the 40 samples (17.5%) were found to have CD33 expression on at least 5% of the NK cells. The CD33-positive NK cell population accounted for an average of 11.4% of NK cells (median 11.9%, range 8.0-15.3%) and 2.2% of total white cells (median 1.1%, range 0.1-10.1%). This NK cell subset expressed bright CD2, bright CD56, and dim CD16. On average, CD33 expression on NK cells was dimmer than on monocytes (mean median fluorescence intensity ratio 0.4; range 0.1-1.0). This study characterizes expression of CD33 on NK cells. Recognition of this pattern of antigen expression is critical in evaluating samples for MRD in patients with myeloid neoplasms, particularly AML.

Flow cytometric detection and quantification of CD56 (neural cell adhesion molecule, NCAM) expression in diffuse large B cell lymphomas and review of the literature

AIM

To report unusual CD56 (neural cell adhesion molecule, NCAM) expression on diffuse large B cell lymphoma (DLBCL).

METHODS AND RESULTS

CD56 expression was first detected and quantified on tissues obtained from five cases of DLBCL by flow cytometry (FC), then confirmed by immunohistochemistry. The CD56 expression pattern was heterogeneous among the cases [the molecular equivalent of soluble fluorochrome (MESF) level ranged from 2214 to 133 466]. All were CD10 and Bcl-6 positive, suggesting their germinal centre origin; one was also CD5 positive. An extranodal presentation occurred in three of five cases.

CONCLUSIONS

CD56 expression in B cell lymphoma is a rare occurrence. FC is able to identify aberrant immunophenotypes that can be useful in the identification and monitoring of B cell lymphoma subtypes. The presence of CD56 reported by the literature on certain DLBCL with extranodal presentation might be related to mechanisms involved in growth and expansion.

Flow cytometry in myelodysplastic syndrome: analysis of diagnostic utility using maturation pattern-based and quantitative approaches

Flow cytometry (FCM) is being increasingly evaluated for the diagnosis of myelodysplastic syndrome (MDS). We employed multiple FCM approaches to assess MDS. Five-color FCM, morphology blind, was done on bone marrow aspirates of 57 suspected MDS and 31 normal controls. Maturation pattern, quantitative FCM for low-grade MDS that awards FCM score, and expression of selected antigens on erythroid cells and CD34(+) blasts were evaluated. FCM results were correlated with clinical and laboratory workup. Patients (n = 57) included proven MDS (n = 14), suspected MDS (n = 13), and non-MDS (n = 30). By pattern-based approach, all proven cases were FCM positive. In suspected MDS, 11 (84.61 %) were positive including morphology-negative cases, and two (15.38 %) were intermediate. In non-MDS cases, 27 of 30 (90 %) were FCM negative, 2 of 30 (6.67 %) intermediate, and 1 of 30 (3.33 %) a hematinic-responsive case, positive. Quantitative parameters that characterized MDS included FCM score of >3, percentage CD34(+) B cells, and expression of CD11b, CD15, and CD56 on myeloblasts. CD71 MFI on CD235a(+) erythroblasts and CD38 MFI on myeloblasts were significantly lower in MDS. The former was present in FCM-intermediate suspected MDS but not FCM-intermediate non-MDS cases. Used in the overall clinical context, both maturation pattern recognition and quantitative approaches, the latter for low-grade MDS, are sensitive methods of diagnosing MDS, including cases negative by morphology and cytogenetics, especially if combined with evaluation of selected antigens, CD71 on CD235a(+) cells and CD38 on CD34(+) cells. The value of FCM in morphology-negative cases needs better definition of specificity through more extensive evaluation of secondary dyspoiesis.

The Expression Pattern of CD56 (N-CAM) in Human Bone Marrow Biopsies Infiltrated by Acute Leukemia

In hematological neoplasms CD56 (N-CAM) is expressed by T/natural killer (NK) cell lymphoma, by most neoplastic plasma cells in multiple myeloma and also in a subset of acute myelogenous leukemias (AML). In the latter, it is an indicator of poor clinical outcome. Most of the data on CD56 expression in acute leukemia have been obtained by flow cytometric analysis. Up to now, no systematic analysis of the expression pattern of CD56 in formalin fixed paraffin embedded bone marrow biopsies of acute leukemias has been performed. We immunohistochemically studied the expression of CD56 in a series of 141 bone marrow biopsies fixed in Sublimat Mercury II Chloride (SUSA) including 100 cases of AML FAB M0-M7, 11 cases of AML not further specified, 3 cases of biphenotypical leukemia, 20 cases of acute lymphoblastic leukemia (ALL) and 7 cases of reactive bone marrow biopsies. Overall, 14 of 134 (10%) leukemia cases were positive for CD56. Detail analysis revealed positivity in 5/13 cases of AML M5 (38%), 3/9 AML M1 (33%), 1/8 AML M0 (13%), 1/11 AML not specified (9%), 2/31 AML M2 (7%) and 2/26 AML M4 (8%). All cases of ALL and biphenotypic leukemias were CD56 negative. The CD56 expression in AML M5 was statistically significant (p = 0.003). On paraffin embedded bone marrow biopsies CD56 expression occurs in de novo AML with an overall frequency of 13%. It is significantly correlated with AML M5, which is positive in 38% of the cases. Cases of ALL are consistently CD56 negative.

Is it important to decipher the heterogeneity of "normal karyotype AML"?

Almost half of adult acute myelogenous leukemia (AML) is normal cytogenetically, and this subgroup shows a remarkable heterogeneity of genetic mutations at the molecular level and an intermediate response to therapy. The finding of recurrent cytogenetic abnormalities has influenced, in a primary way, the understanding and treatment of leukemias. Yet "normal karyotype AML" lacks such obvious abnormalities, but has a variety of prognostically important genetic abnormalities. Thus, the presence of a FLT3-ITD (internal tandem duplication), MLL-PTD (partial tandem duplication), or the increased expression of ERG or EVI1 mRNAs confer a poor prognosis, and an increased risk of relapse. In contrast, the presence of cytoplasmic nucleophosmin or C/EBPA mutations is associated with lower relapse rates and improved survival. Although resistance to treatment is associated with specific mutations, the degree to which the leukemia resembles a stem cell in its functional properties may provide greater protection from the effects of treatment. Although usually all of the circulating leukemia cells are cleared following treatment, a small residual population of leukemic cells in the bone marrow persists, making this disease hard to eradicate. Increased understanding of the biological consequences of at least some of these mutations in "normal karyotype AML" is leading to more targeted approaches to develop more effective treatments for this disease.

Flow cytometric analysis of myelomonocytic cells by a pattern recognition approach is sensitive and specific in diagnosing myelodysplastic syndrome and related marrow diseases: Emphasis on a global evaluation and recognition of diagnostic pitfalls

Published data on flow cytometry (FCM) in diagnosing myelodysplastic syndromes (MDS) varies greatly in analytic methods and interpretational approaches. We tested the diagnostic utility of the pattern recognition approach by a retrospective review of 180 MDS, 31 myelodysplastic/myeloproliferative disease (MDS/MPD), 37 non-MDS cytopenia and 20 myeloproliferative disease (MPD) cases. Cases were placed into "positive", "intermediate", and "negative" FCM categories based upon the antigenic aberrations observed on myelomonocytic cells. By exclusion or inclusion of the intermediate category as indicative of MDS or MDS/MPD, the overall sensitivity and specificity were 84% and 97% or 98% and 78%, respectively. The overall abnormalities detected by FCM correlated with the severity of morphological dysplasia and clonal cytogenetic abnormalities. MPD also demonstrated immunophenotypic aberrancy. Based on a global evaluation of myelomonocytic abnormalities, and recognition of diagnostic pitfalls and caveats, the pattern recognition approach of FCM is sensitive and reliable in diagnosing MDS and related myeloid diseases.

Myeloid Malignancies: Myelodysplastic Syndromes, Myeloproliferative Disorders, and Acute Myeloid Leukemia

As hematopoietic cells proceed in differentiation from stem cells to committed progenitors to later stage mature forms, they undergo a sequence of morphologic, immunophenotypic, and functional changes that are a consequence of interaction between the underlying cellular genetic program and environmental cues, are linear for each cell lineage, and result in a pattern of antigenic expression related to lineage and stage of maturation. The antigenic patterns characteristic of normal maturation have been elucidated systematically and found invariant between individuals. Deviation from this pattern is a hallmark of hematopoietic neoplasia. Application of these principles to myelodysplastic syndromes, myeloproliferative disorders, and acute myeloid leukemia is presented and illustrated.

CD56-Positive Large B-cell Lymphoma

CD56 (NCAM), a neural adhesion molecule, is normally expressed on natural killer cells and subsets of T cells and is commonly seen on hematolymphoid neoplasms such as plasma cell myeloma and acute myelogenous leukemia. It is uncommon in B-cell lymphoma. From 2001 to 2003 a cohort of 20 cases of CD56 B-cell lymphomas was identified by flow cytometry (<0.5% of all B-cell lymphomas studied) during a 2-year period. Most (90%) expressed CD10 and 5/5 tested cases were BCL6, suggesting a follicular origin. An extranodal disease presentation was seen in 45% and may be related to CD56 expression. These CD56 B-cell lymphomas may represent a new subset of large B-cell lymphoma. The relationship of cells with this antigenic profile to normal B-cell differentiation is explored.

CD56-positive acute lymphoblastic leukemia

We report a patient with lung cancer who developed CD56-positive acute lymphoblastic leukemia. He was referred to our hospital for thrombocytopenia. Atypical cells were found in the blood and the bone marrow. These cells were immunophenotypically positive for CD3epsilon, CD56, and terminal deoxynucleotidyl transferase, and negative for surface CD3, CD4, CD19, CD33, and myeloperoxidase. A small proportion of leukemic cells express CD13. There were no rearrangements of T-cell receptor (TCR)-beta, TCR-gamma, or immunoglobulin heavy chain. No Epstein-Barr virus was detected. Systemic examination did not detect any tumors other than pulmonary adenocarcinoma, and the patient was diagnosed as having acute natural killer (NK) cell leukemia. Chemotherapy was effective, and he achieved complete remission. The course of the disease was complicated by a lung abscess, and the patient died 3 months after the diagnosis. We considered that the diagnosis was blastic NK cell lymphoma/leukemia subtype. However, it actually was myeloid/NK cell precursor leukemia subtype that weakly expressed CD13.

A der(19)t(12;19)(q12;p13.3) in a case of pediatric acute leukemia with unusual immunophenotype

We describe a case of acute leukemia in a child with an unusual immunophenotype and a novel cytogenetic abnormality. The leukemia blasts expressed myeloid, natural killer and B-lineage associated antigens. Cytogenetics showed the presence of a novel unbalanced chromosomal translocation, der(19)t(12;19)(q12;p13.3). The patient achieved and maintained remission with myeloid-directed chemotherapy. The differential diagnosis of the immunophenotype and the potential fusion genes are discussed.

Natural killer cell neoplasms

Lymphoid neoplasms that are derived from natural killer (NK) cells are uncommon but distinct clinicopathologic disease entities. Three types have been recognized and categorized in the latest World Health Organization classification: extranodal NK cell lymphoma, nasal-type; aggressive NK cell leukemia; and blastic NK cell lymphoma. All NK tumor cells express the NK cell marker CD56, but they lack the expression of surface CD3 and the rearrangement of T-cell receptor genes, which distinguish them from T-lymphoid neoplasms. There is also a strong association with the Epstein-Barr virus, except in blastic NK cell lymphoma. Extranodal involvement by the NK cell tumor is common, especially in the nasal cavity, the skin, and the gastrointestinal tract. All 3 NK cell neoplasms are characterized by aggressive clinical course and poor response to treatment. Although the optimal treatment modality remains to be determined, good initial response to combined radiation therapy and chemotherapy has been observed in localized disease. Further studies in the basic biology of the NK cell and the pathology of NK cell neoplasms may shed light on the development of newer and more effective therapy.

Using 4-color flow cytometry to identify abnormal myeloid populations

CONTEXT

The diagnosis of myeloproliferative disorders (MPDs) and myelodysplastic syndromes (MDSs) has historically relied on combining clinical information with the morphologic features of the peripheral blood and bone marrow to reach a final diagnosis. Objective evidence of a myeloid stem cell neoplasm in the form of a clonal cytogenetic abnormality is provided in only 30% to 40% of the non-chronic myeloid leukemia (CML) chronic MPDs (non-CML MPDs) and in a similar percentage of the MDSs.

OBJECTIVE

To identify normal patterns of antigen expression during myeloid maturation and to determine whether flow cytometric evaluation of myeloid maturation represents an additional objective way to assess the likelihood of a stem cell neoplasm.

DESIGN

We retrospectively evaluated 4-color flow cytometry data from more than 400 bone marrow aspirates obtained since 1998 from patients suspected of having a non-CML MPD or an MDS.

RESULTS

Reproducible patterns of antigen expression were seen in normal myeloid maturation as well as in benign reactive settings such as marrow regeneration. In addition, we summarize data, presented in detail elsewhere, from a retrospective comparison of the sensitivity of flow cytometry with conventional cytogenetics for a large number of bone marrow aspirates on which both types of studies were performed. These data indicate that more than 90% of non-CML MPD and MDS cases with a clonal cytogenetic abnormality will be identified as abnormal by 4-color flow cytometry, and they therefore validate the use of flow cytometry in the diagnosis of these disorders.

CONCLUSIONS

In experienced laboratories, 4-color flow cytometry represents a valuable addition to the workup of non-CML MPDs and MDSs.

Evidence for expression of early myeloid antigens in mature, non-blast myeloid cells in myelodysplasia

Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders with frequent cytogenetic abnormalities. They can arise de novo or be related to therapy. Although blasts in MDS have been studied extensively, there is little information available on the mature, non-blast myeloid cells (NBMCs). We used a retrospective case-control study design. NBMC populations in MDS (48 cases) and in tumor-free control (12 cases) bone marrow samples were analyzed using multiparameter flow cytometry for mean side scatter (SSC) channel number and for expression of aberrant cell surface antigens. MDS cases were stratified on the basis of cytogenetic abnormalities. We report that NBMCs in MDS with normal karyotype expressed significantly higher HLA-DR than controls (P = 0.034). NBMCs in MDS cases with cytogenetic abnormalities and with > or =5% marrow blasts, compared with controls, had significantly higher CD34 and higher HLA-DR but lower CD10 and lower SSC mean channel number. CD34 expression in NBMCs was significantly greater in therapy-related MDS compared with de novo MDS ( P = 0.01), although the presence of cytogenetic abnormalities was not different ( P > 0.05). These data suggest that bone marrow, mature, NBMCs have phenotypic changes in MDS that are not seen in normal controls.

New developments in anti-tumor efficacy and malignant transformation of human natural killer cells

For decades, the driving force behind many immunologic studies has been the hope of augmenting anti-cancer therapy through targeted immune-based strategies. The question remains: can immune cells be successfully manipulated to augment chemotherapy and aid in the elimination of malignancy? Such efforts have included work with natural killer (NK) cells, large granular lymphocytes that contribute to the early innate immune response by nonspecifically killing pathogens, virus-infected cells, and tumor cells, and by producing important early immunoregulatory cytokines such as interferon gamma (IFN-gamma). These qualities have made NK cells attractive candidates for therapy aimed at boosting host immunity against tumor cells and infectious pathogens. Recent advances in our understanding of how NK cells select targets for killing have improved our ability to design and test more effective immune-targeted therapies. However, our understanding of NK leukemias and lymphomas remains incomplete. NK leukemias and lymphomas, while rare, represent a significant challenge to the patients and physicians coping with them, as most lack effective treatment strategies. This brief review will summarize current directions in NK cell immune therapy and give an update on the classification and treatment of NK malignancies.

Antigen expression patterns reflecting genotype of acute leukemias

Multi-parameter flow cytometry, molecular genetics, and cytogenetic studies have all contributed to new classification of leukemia. In this review we discuss immunophenotypic characteristics of major genotypic leukemia categories. We describe immunophenotype of: B-lineage ALL with MLL rearrangements, TEL/AML1, BCR/ABL, E2A/PBX1 translocations, hyperdiploidy, and myc fusion genes; T-ALL with SCL gene aberrations and t(5;14) translocation; and AML with AML1/ETO, PML/RARalpha, OTT/MAL and CBFbeta/MYH11 translocations, trisomies 8 or 11 and aberrations of chromosomes 7 and 5. Whereas some genotypes associate with certain immunophenotypic features, others can present with variable immunophenotype. Single molecules (as NG2, CBFbeta/SMMHC and PML/RARalpha proteins) associated with or derived from specific translocations have been described. More often, complex immunophenotype patterns have been related to the genotype categories. Most known associations between immunophenotype and genotype have been defined empirically. Therefore, these associations should be validated in independent patient cohorts before they can be widely used for prescreening of leukemia. Progress in our knowledge on leukemia will show how the molecular-genetic changes modulate the immunophenotype as well as how the expressed protein molecules further modulate cell behavior.

CD56+, NKp46+ cell line (MZ93) expressing T-cell and myeloid antigens

The MZ93 cell line, established from a patient with CML, expressed CD4, CD7, CD13, CD25, CD33, CD34, CD56 and NKp46. The additional karyotype abnormality of the Ph-positive leukemia cells in vivo, 6p+, was also observed in MZ93. The early passages of MZ93 expressed CD3 in the cytoplasm, but the late passages did not. The cells did not express mature NK-markers as expected. The messenger RNAs of CD2 and NKp46 were detected and those of CD3varepsilon and CD3zeta were absent in the cells. Therefore, the cell line has the immunophenotype likely to NK and/or T cell precursor.

CD56 expression in myeloperoxidase-negative FAB M5 acute myeloid leukemia

CD56 is a natural killer (NK) cell marker that has been identified in approximately 15-20% of acute myeloid leukemia (AML) cases, where it has been associated with monocytic morphology and chromosomal abnormalities such as trisomy 8, t(8;21), t(15;17), and 11q23 rearrangements. The clinical presentation, chromosomal abnormalities as detected by fluorescent in-situ hybridization (FISH), and clinical outcomes of 7 patients with AML are presented. These cases were characterized by French-American-British (FAB) M5 morphology, myeloperoxidase (MPO) negativity, and co-expression of myelomonocytic and NK cell-associated antigens (CD11c(+), CD13(+), CD15(+), CD33(+), HLA-DR(+), and CD56(+)). All patients presented lymph node, hepatic, or splenic involvement at diagnosis. Despite the homogeneous morphologic and immunophenotypic characteristics the outcomes varied considerably. Two patients died during induction therapy, but the other five patients attained complete remission (CR). Of these five patients, 4 have received a bone marrow transplantation (autologous or allogeneic) and 3 of them are in CR (median follow-up: 45 months). The three patients with 11q23 rearrangements had a poor outcome and died of their disease within 1 year of diagnosis. Further studies with a larger group of patients would help establish the actual prognostic value of these morphologic, immunophenotypic and cytogenetic features.

CD56+ blastic transformation of chronic myeloid leukemia involving the skin

We report on two patients with chronic myeloid leukemia (CML) who presented blastic transformation involving the skin, with leukemic infiltrates showing unusual morphologic and immunohistologic characteristics. Both patients were elderly men with a 36-month and a 40-month history of CML, respectively. They presented with disseminated, reddish to violaceous papules and plaques (case 1), and with localized reddish nodules on the left temporal area (case 2). Concurrent features of blastic transformation in the bone marrow were observed in one patient (case 1). Histopathologic examination of skin lesions revealed similar features in both cases. There was a moderate to dense dermal infiltrate composed mainly of medium-sized atypical mononuclear myeloid precursor cells with only few relatively well-differentiated cells of the granulocytic series. Histochemical staining for naphthol-ASD-chloroacetate esterase revealed strong positivity (>50% of neoplastic cells) in case 2 and only scattered positivity (< 10% of neoplastic cells) in case 1. Immunohistologic analysis performed on paraffin-embedded sections showed in both cases variable reactivity of neoplastic cells for leucocyte common antigen (CD45), lysozyme, myeloperoxidase, CD11c, CD15, CD43, CD66, CD68, HLA-DR, and the neural cell adhesion molecule (NCAM) CD56. A negative reaction was observed for CD3, CD34, and TdT. The immunohistologic findings were remarkably similar to those reported for acute myeloid leukemia (AML) with monocytic differentiation (French-American-British [FAB] classification, subtype M4). Examination of blasts from the bone marrow performed in one patient (case 1) revealed a similar phenotype also with CD56 expression. In conclusion, our observations show that specific cutaneous infiltrates in CML may show morphologic and immunohistochemical characteristics similar to those observed in AML with monocytic differentiation. Moreover, specific cutaneous manifestations of CML may express CD56.

Lineage switch in childhood leukemia with monosomy 7 and reverse of lineage switch in severe combined immunodeficient mice

Morphophenotypic lineage switches occur in a small percentage of those with acute leukemia, and the underlying mechanisms are not clear. In this study, we attempted to induce a lineage switch in acute myelocytic leukemia (AML) with monosomy 7, whose lineage had switched from acute T-lymphocytic leukemia (T-ALL) during chemotherapy, in severe combined immunodeficient (SCID) mice. Although the transplanted myeloid cells were engrafted in SCID mice without cytokine administration, T-ALL developed in SCID mice treated with recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. Analysis of the nucleotide sequences of the rearranged T-cell receptor gamma-chain (TCR-gamma) gene revealed that this lineage switch resulted from the selection of the T-lineage subclone in SCID mice, which had expanded at onset. In addition, we found that the T-lineage and myeloid cells belonged to the distinct subclones, which were different in TCR-gamma gene rearrangements, but were derived from a common clone with an identical N-ras gene mutation for both subclones. In in vitro cultures, only the myeloid subclone grew; the T-lineage subclone failed to grow even in the presence of recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. These results suggested that the initial diagnostic T-lymphoid subclone, whose growth was dependent on these cytokines and the hematopoietic microenvironment, emerged from a bipotential T-lymphoid/myeloid leukemic stem cell, and further genetic event(s) induced the myeloid subclone, which grew independently of these cytokines and the microenvironment.

Comprehensive review of adult acute myelogenous leukemia: cytomorphological, enzyme cytochemical, flow cytometric immunophenotypic, and cytogenetic findings

This study reports findings from a retrospective, comprehensive review of 80 cases of adult AML in regard to cytomorphology, enzyme cytochemistry (EC), flow cytometric immunophenotyping (FCI), and chromosomal analysis. From this review, we conclude that diagnostically challenging cases can only be subtyped by combining the cytomorphology with EC, FCI, and subsequent cytogenetic results. This is particularly true in recognizing the hypogranular variant of AML,M3 (AML, M3m) and distinguishing it from other subtypes. Nonlineage expression of markers (CD1, CD2, CD4, CD5, CD7, and CD56) was nonspecific as to AML subtype. Of interest, CD2 coexpression in acute myelomonocytic leukemia with eosinophilia (M4-Eo) was exclusively associated with inversion of chromosome 16 (inv 16) and was not observed in the other M4-Eo's without inv16. We also recognized a previously undescribed M3m with CD56 coexpression, heightening awareness of this entity which needs to be distinguished from the unique subtype of CD56+ AML with otherwise similar immunophenotypic and morphologic characteristics. In addition, nonlineage expression of CD19 alone was exclusively associated with the cytogenetic finding of t (8;21) (q22; q22) and thus may represent a favorable prognostic indicator by FCI.

Specific skin manifestations in CD56 positive acute myeloid leukemia

We found 16 CD56+ cases (29.6%) among 54 acute myeloid leukemia (AML) patients; they showed significantly frequent cutaneous involvement compared to CD56- cases (43.8% vs. 15.8%, p<0.05). Four of the CD56+ AML cases with specific skin manifestations were reviewed histologically. In all cases, cutaneous leukemic cells were seen in the dermis and subcutaneous tissue with accentuation around the adnexa/nerve, but sparing the epidermis. In addition, angiocentric/ angiodestructive and prominent cohesive tumor cell growth were seen in two cases, respectively. These findings suggest that the expression of CD56 may often be associated with the cutaneous involvement in AML, and that the above histological findings should remind us of the possibility of specific skin manifestations in CD56+ AML.

CD56 expression in acute promyelocytic leukemia: a possible indicator of poor treatment outcome?

PURPOSE

Blast expression of CD56 is frequent in patients with t(8;21)(q22;q22) acute myeloid leukemia and is associated with an inferior outcome. The expression of CD56 has rarely been reported in acute promyelocytic leukemia (APL) and has not been clinically characterized. Therefore, we examined the prognostic significance of CD56 expression in APL.

PATIENTS AND METHODS

We identified all reported cases of CD56+ APL in the medical literature and collected clinical, biologic, and therapeutic details.

RESULTS

Data were obtained for 12 patients with CD56+ APL (> 20% blast expression of CD56), including four cases from a single institution with a total of 42 APL patients. All of the CD56+ APL patients had documented cytogenetic presence of t(15;17), and of the nine reported isotypes, eight (89%) were S-isoform. Only six CD56+ patients (50%) attained complete remission (CR); the other six individuals died within 35 days of presentation. Of the six patients who attained a CR, three (50%) relapsed at 111, 121, and 155 weeks, whereas three remained in continuous CR at 19, 90, and 109 weeks. Comparison of the control CD56- to CD56+ APL patients demonstrated that the latter group had a significantly lower fibrinogen level (P = .007), and among patients for whom data were available, there was a higher frequency of the S-isoform (P = .006). Additionally, the CR rate (50% v 84%, P = .025) and overall median survival (5 v 232 weeks; P = .019) were significantly inferior for CD56+ APL patients.

CONCLUSION

CD56+ acute promyelocytic leukemia is infrequent, seems to occur more frequently with the S-isoform subtype, and may be associated with a lower CR rate and inferior overall survival.