Aberrant expression of CD7, CD56, and CD79a antigens in acute myeloid leukemias

The prognostic significance of selected markers of leukemic cells is well known. CD7 and CD56 expression at diagnosis has been associated with low remission rates and biological aggressiveness in a significant proportion of acute leukemias. Among 46 patients with acute myeloid leukemia, we found CD7 expression in 15 cases (32.6%) and CD56 positivity in 10 patients (21.7%). Six of these myeloid leukemia cases (13%) showed expression of both CD7 and CD56. Four of 46 (8.7%) patients expressed CD79a. Among the 10 that were acute myeloblastic leukemia, 8 expressed CD7, 4 expressed CD56, and 4 were positive for CD79a. Thus, these markers were expressed early in hemopoietic ontogeny in the lesser-differentiated acute myeloid leukemia subtypes, including FAB M0, M1, and M2. Whereas CD7 and CD56 were each positive in 4 cases of acute myelomonocytic leukemia (FAB M4 subtype), there was no CD79a expression in the M4 cases. CD7 is expressed by mature T cells, NK cells, and an immature myeloid cell subset. NK cells and a T cell subset express CD56. By contrast, CD79a is a B cell marker that is assigned a high score of 2.0 in the differentiation of acute leukemias of ambiguous lineage in the WHO classification. The aberrant expression of CD7, CD56, and CD79a, representing the capacity of these leukemias for trilineal expression of leukocyte differentiation antigens, portends a poor prognosis.     

Immunophenotyping of acute leukemias: diagnostic and pronostic utility in Abidjan, Côte d'Ivoire

Flow cytometry is nowadays the first-line method for immunophenotypic identification of blast cells but is not so usual in limited-resources countries. We have investigated on the usefulness of this tool in Abidjan, C?te d'Ivoire. Bone marrow sample from 13 patients with acute leukemia identified by cytology and cytochemical analysis was immunophenotyped by using monoclonal antibodies directed to: T lymphoid cells (CD3, CD5, CD7); B lymphoid cells (CD10, CD19, CD20, CD22, HLA-DR) and myeloid cells (CD13, CD33). Immunophenotyping allowed us to confirm the diagnosis of 6 de novo acute leukemias (2 acute myeloid leukaemias, 4 acute lymphoid leukemias) and 7 acute leukaemias resulting from chronic myeloid leukaemias. Immunophenotyping also characterizes the atypical/aberrant lineage essential for the prognosis: 2 biphenotypic acute leukemias (myeloid/lymphoid T) were identified. Our results suggest that flow cytometry may be a useful additional tool to identify the specific leukemic cell, to make a better classification as well as a prognosis evaluation of patients with acute leukemias.     

Usefulness of anti-CD117 in the flow cytometric analysis of acute leukemia

We assessed the diagnostic usefulness of adding anti-CD117 to our existing flow cytometric profile in the analysis of 150 consecutive cases of acute leukemia (de novo or relapsed acute myelogenous leukemia [AML], AML arising in myelodysplastic syndrome, blast crisis of chronic myelogenous leukemia [CML], acute lymphoblastic leukemia, acute unclassifiable leukemia, and biphenotypic leukemia). CD117 was expressed on more than 10% of blasts in 64% of de novo AMLs (42/66), 95% of relapsed AMLs (19/20), 75% of AMLs arising from a myelodysplastic syndrome (6/8), and 25% of myeloid blast crisis in CMLs (1/4). CD117 was not expressed in acute lymphoblastic, acute biphenotypic, or unclassified leukemia or lymphoid blast crisis of CML. The specificity, positive predictive value, sensitivity, and negative predictive value of CD117 for AML were 100%, 100%, 69%, and 62%, respectively. CD117 is a specific marker for myeloblastic leukemias. Sensitivity is greatest in French-American-British M2 and relapsed AML. Intensity of CD117 expression is dim. Despite the high specificity and positive predictive value, the addition of anti-CD117 to our panel did not prove essential for the assignment of blast lineage.     

Biphenotypic acute leukemia with coexpression of CD79a and markers of myeloid lineage

Acute leukemias demonstrating immunophenotypic features of more than 1 cell lineage are referred to as acute leukemias of ambiguous lineage in the new World Health Organization classification system. A subtype of leukemia of ambiguous lineage is biphenotypic acute leukemia in which the malignant cell population expresses markers of 2 different lineages, most commonly myeloid and either B- or T-lymphoid lineages. This entity has been defined by a scoring system proposed by the European Group for the Immunological Characterization of Acute Leukemias (EGIL), with various markers assigned a score of 2, 1, or 0.5 depending on their specificity for myeloid or lymphoid lineage. Those cases having a score greater than 2 for the myeloid and either the B- or T-lymphoid lineages are biphenotypic acute leukemia in this system. One marker, CD79a, has been so clearly associated with acute lymphoblastic leukemia (ALL) by some researchers that its expression in the presence of blast markers is considered indicative of B-ALL. We describe an unusual case of acute leukemia meeting the criteria for biphenotypic acute leukemia in which CD79a expression was observed in the blast population.     

Leukemias resembling acute promyelocytic leukemia, microgranular variant

Acute promyelocytic leukemia (APL) should be distinguished from other subtypes of acute myeloid leukemia (AML) because of the increased risk of disseminated intravascular coagulation (DIC) and its response to arsenic compounds and retinoids. Some cases of AML seem morphologically similar to the microgranular variant of APL (French-American-British [FAB] AML-M3v) but lack the t(15;17). We evaluated 8 cases of APL-like leukemias for subtle morphologic, cytochemical, immunophenotypic, and cytogenetic differences compared with 5 cases of promyelocytic leukemia/retinoic receptor alpha (PML/RARalpha)-positive APL (FAB AML-M3v). We also evaluated both groups for the presence of DIC. No differences among the groups were noted in blast size, chromatin pattern, nuclear morphologic features, intensity of myeloperoxidase staining, or presence of Auer rods. Immunophenotypes were similar; both types of cases lacked CD34 and HLA-DR and were CD13+ and CD33+. Two cases of APL-like leukemias also were CD56+. DIC was present in 2 patients with M3v. Our study shows that there are no definitive morphologic, cytochemical, or immunophenotypic findings that can distinguish these cases from PML/RARalpha-positive APL.     

A hybrid form of myeloid/NK-cell acute leukemia and myeloid/NK-cell precursor acute leukemia

Natural killer (NK)-cell leukemia/lymphoma is a rare entity that has been defined only in recent years. In the Revised European-American Lymphoma and World Health Organization classifications, only the mature NK-cell malignancies are included. However, at least 3 types of precursor NK-cell neoplasms have been reported in the literature. These include myeloid/NK-cell acute leukemia, myeloid/NK-cell precursor acute leukemia, and blastic NK-cell lymphoma/leukemia. These leukemias are characterized by the presence of blasts, which express CD56, in the peripheral blood, bone marrow, lymph nodes, and/or extranodal tissues. We report a case that is morphologically consistent with myeloid/NK-cell acute leukemia but immunologically is myeloid/NK-cell precursor acute leukemia. This case is unique in its cutaneous presentation without involvement of the peripheral blood. Extensive flow cytometric studies were performed on the skin biopsy and bone marrow aspirate specimens, which included many markers that had not been tested before in these entities. The clinical implications of these findings are discussed.     

Diagnostic challenges related to myeloid/natural killer cells, a variant of myeloblasts

The authors report herein two diagnostically challenging cases centered on the myeloid/natural killer (myeloid/NK) cells, a variant of myeloblasts, to illustrate the importance of advanced flow cytometric immunophenotyping and an updated understanding of surface markers in hematopoietic malignancies. Myeloid/NK cell acute leukemia is a very rare subtype of leukemia. Although its NK-cell nature is debatable, it represents a variant of leukemia with distinct morphological and immunophenotypical features. The first case is a de novo myeloid/NK-cell acute leukemia with a striking clinical, morphologic and immunophenotypic resemblance to acute promyelocytic leukemia (APL), but which could be distinguished by its CD11a, CD18, CD117 and CD9 expression. This case illustrates the importance of utilizing the APL surrogate surface phenotype of HLA-DR(low), CD11a(low) and CD18(low) by flow cytometric study to rule in/out APL immunophenotypically. In the second case, we show that myeloid/NK-cell blasts can present as a variant of blasts in a preleukemic disease as refractory anemia with excess blasts-1 (RAEB-1), where the blasts were negative for CD34, CD117 and HLA-DR. The recognition of such blast variant is important in appropriately classifying such preleukemic diseases by blast percentage.     

CD56+/CD4+ lymphomas and leukemias are morphologically, immunophenotypically, cytogenetically, and clinically diverse

CD56, a neural adhesion molecule, is a marker of natural killer (NK) lymphocytes as well as a subgroup of CD8+ T cells. Normal lymphocytes with a CD56/CD4 phenotype are scarce. Physiologic increases may occur in patients with immunosuppression, chronic inflammation, and autoimmune disorders. We report 4 cases of lymphomas/leukemias with the unusual CD56/CD4 phenotype. Two were of T-cell and 2 of true NK-cell origin. The T-cell lymphomas had large granular lymphocyte morphologic features and splenomegaly. One patients had a benign course; the other died within months of the leukemia diagnosis. The 2 NK cell lymphomas had blastic morphologic features, initially involved skin, and had a very aggressive clinical course; 1 patient died of acute leukemia, and 1 had recurrence after bone marrow transplantation. Cytogenetic analyses did not show a consistent pattern of abnormalities. The NK lymphoma with acute leukemia had a t(2;5) but was CD30- and anaplastic lymphoma kinase negative. Although CD56+/CD4+ lymphomas/leukemias are a heterogeneous group, there may be a distinct subgroup of NK lymphoblastoid lymphomas of the skin, judging from our cases, as well as those previously reported.     

NRP-1/CD304 expression in acute leukemia: a potential marker for minimal residual disease detection in precursor B-cell acute lymphoblastic leukemia

Neuropilin-1 (NRP-1)/CD304 is a marker for plasmacytoid dendritic cells. We determined the distribution of NRP-1/CD304 expression on normal hematopoietic cells and in 167 acute leukemias by flow cytometry. NRP-1/CD304 surface expression was frequent in precursor B-cell acute lymphoblastic leukemia (36/51 [71%]) and uncommon in acute myeloid leukemia (22.9%). In acute myeloid leukemia, expression was noted in all (4/4) acute myeloid leukemias with the M4eo subtype and in 50% of specimens (6/12) with complex cytogenetics. On hematopoietic cells, NRP-1/CD304 was expressed on normal erythroid progenitors, plasma cells, and B-cell progenitors, as well as plasmacytoid dendritic cells. Expression was not consistently detected on other hematopoietic cell types. Owing to this distribution of expression, the detection of NRP-1/CD304 alone on a hematopoietic cell cannot be used to determine plasmacytoid dendritic cell differentiation. Finally, we show that NRP-1/CD304 is overexpressed in 30% of precursor B-cell acute lymphoblastic leukemia samples compared with normal B-cell progenitors, allowing for its potential use as a marker for the detection of minimal residual disease.     

Histologic and immunohistologic characterization of skin localization of myeloid disorders: a study of 173 cases

A retrospective analysis of 173 skin biopsy specimens of myeloid leukemia cutis (MLC) was performed to determine histologic and immunophenotypic criteria that could distinguish the varied myeloid disorders from one another. For the study, 11 relevant histologic items were scored and 12 antigens were studied (CD68 [KP1], CD163, CD14, CD4, myeloperoxidase [MPO], CD33, CD117, CD34, CD56, MIB-1, CD303, and CD123). Underlying myeloid disorders were essentially acute myeloid leukemias (65.3%), chronic myelomonocytic leukemias (11.0%), and refractory anemia (10.4%). Skin lesions were de novo in 7.5%, concurrent in 26.6%, and subsequent in 60.7%. Several morphologic characteristics (density, size of tumor cells, inflammatory background) were statistically useful in distinguishing between varied myeloid disorders. De novo MLCs displayed a specific morphologic profile. Association of CD68, CD33, and MPO could diagnose 100% of the cases of MLC. However, the immunohistochemical panel could not distinguish between the varied underlying myeloid disorders, with the exception that CD123 was particularly powerful in recognizing chronic myelomonocytic leukemia and also permitted reclassification of 4 cases as blastic plasmacytoid dendritic cell neoplasm.     

Acute myeloid leukemia: immunohistologic findings in paraffin-embedded bone marrow biopsy specimens.

Immunohistochemical investigations were performed on decalcified, paraffin-embedded iliac crest trephine biopsy specimens from 30 cases of acute myeloid leukemia (AML, as defined by the FAB classification) with antibodies against B cells (L26, 4KB5, MB1, Ki-B3), T cells (UCHL1, MT1), myeloid/histiocytic cells (anti-neutrophil elastase, MAC387, anti-S-100 protein, anti-alpha 1-antichymotrypsin, DAKO-M1), natural killer/killer cells (anti-Leu-7), and megakaryocytes (anti-factor VIII-related antigen). (1) The blast cells of all the cases reacted with from at least two to at most eight different antibodies. Each antibody reacted with blast cells in a minimum of two (maximum 30) cases. (2) MT1, Ki-B3, anti-alpha 1-antichymotrypsin anti-neutrophil elastase, anti-S-100 protein, and MAC387 stained blast cells in more than 50% of the cases; MB1, L26, UCHL1, 4KB5, and DAKO-M1 in 20% to 50% of the cases; and anti-Leu-7 and anti-factor VIII-related antigen in less than 20% of the cases. (3) In the majority of cases many T lymphocytes, a small-to-moderate number of B lymphocytes, and a few Leu-7-positive lymphoid cells were intermingled with the blast cells. In some cases, especially where only a minor proportion of the blast cells was immunostained, it was nearly impossible to distinguish the lymphocytes of the tumor's stromal reaction from small blast cells. Thus, AML exhibits a heterogeneous immunophenotype in trephine biopsy specimens. Immunohistologic diagnosis of this disease in such specimens may be extremely difficult. Since staining of the blast cells with one or more of the antibodies generally used to define B cells, T cells, or their neoplastic derivatives is not uncommon, misinterpretation as non-Hodgkin's lymphoma of high-grade malignancy could easily occur. These findings also suggest that mixed-type (hybrid) acute leukemias with coexpression of myeloid and lymphoid cell markers could be more common than generally realized.     

Expression of leukemia-associated antigen, JL1, in bone marrow and thymus

The identification of immunophenotypic markers with restricted expression has long been a critical issue in diagnostic and therapeutic advances for acute leukemias. We previously developed a monoclonal antibody against a new thymocyte surface antigen, JL1, and showed that JL1 is expressed in the majority of acute leukemia cases. In this study, using multiparameter flow cytometric analyses, we found that JL1 was uniquely expressed in subpopulations of normal bone marrow (BM) cells, implying the association of JL1 with the differentiation and maturation process. Although CD34(+) CD10(+) lymphoid precursors and some of maturing myeloid cells express JL1, neither CD34(+) CD38(-/lo) nor CD34(+) AC133(+) noncommitted pluripotent stem cells do. As for the myeloid precursors, CD34(+) CD33(+) cells do not express JL1. During lymphopoiesis, JL1 on the earliest lymphoid precursors disappear in the CD20(+) sIgM(+) stage of B-cell development or after CD1a down-regulation in thymocytes. Despite the highly restricted expression of JL1 in normal BM cells, most of the leukemias express JL1 irrespective of their immunophenotypes. These results indicate that JL1 is not only a novel differentiation antigen of hematopoietic cells, but also a leukemia-associated antigen. Therefore, we suggest that JL1 be a candidate molecule in acute leukemia for the diagnosis and immunotherapy that spares the normal BM stem cells.     

Hand mirror variant of adult acute lymphoblastic leukemia. Evidence for a mixed leukemia.

Blast cells from a female patient with acute lymphoblastic leukemia-hand mirror variant were examined using various techniques, including light and ultrastructural morphologic examination, cytochemical analysis, surface antigen characterization, cytogenetic analysis, and gene rearrangement studies. The blast cells were found to be pre-B cells (CD19+ and Tdt+) that also expressed the myeloid antigens CD13 and CD33 and demonstrated a heavy chain immunoglobulin gene rearrangement. Cytogenetic studies revealed a t(11;19) translocation previously described in biphenotypic leukemias. A subset of acute lymphoblastic leukemia-hand mirror cells has been previously defined and includes predominately female patients with an indolent course. The authors' findings place this case, a mixed leukemia, within that subgroup. The possibility of mixed lineage should be considered in future cases of hand mirror variants of adult acute lymphoblastic leukemia. Furthermore, hand mirror morphologic features in any case of acute leukemia should alert the hematopathologist/hematologist to the possibility of mixed lineage.     

CD79 alpha expression in acute myeloid leukemia. High frequency of expression in acute promyelocytic leukemia.

CD79 alpha is a subunit of an intracytoplasmic protein reported to be specific for B lymphocytes, including immature B lineage cells. To evaluate expression of the CD79 alpha antigen in acute myeloid leukemia (AML), we studied forty-eight cases of AML by paraffin section immunohistochemistry. The cases included four MO, nine M1, nine M2, ten M3, ten M4, and six M5 AMLs using criteria of the French-American-British cooperative group. Eleven cases demonstrated cytoplasmic staining for the CD79 alpha antigen, including one M1, nine M3, and one M5 AML. These CD79 alpha-positive cases represented 5% of all non-promyelocytic AMLs and 90% of all acute promyelocytic leukemias studied. All acute promyelocytic leukemias had the characteristic t(15;17)(q24;q21), including two cases of the microgranular variant (M3v). No other B-lineage-associated antigens were found in the CD79 alpha-positive cases, with the exception of a subpopulation of CD19-positive leukemic cells in one patient. The two non-promyelocytic leukemias that expressed CD79 alpha had no evidence of t(15;17) and did not express any additional B-lineage-associated antigens that might suggest a mixed lineage proliferation. This study demonstrates that CD79 alpha expression in acute leukemia is not restricted to B-lineage acute lymphoblastic leukemias and that CD79 alpha expression is frequently associated with t(15;17) acute myeloid leukemia.     

Acute leukemias of ambiguous lineage

The 2008 edition of the WHO Classification of Tumors of Haematopoietic and Lymphoid Tissues recognizes a special category called "leukemias of ambiguous lineage." The vast majority of these rare leukemias are classified as mixed phenotype acute leukemia (MPAL), although acute undifferentiated leukemias and natural killer lymphoblastic leukemias are also included. The major immunophenotypic markers used by the WHO 2008 to determine the lineage for these proliferations are myeloperoxidase, CD19, and cytoplasmic CD3. However, extensive immunophenotyping is necessary to confirm that the cells indeed belong to 2 different lineages or coexpress differentiation antigens of more than 1 lineage. Specific subsets of MPAL are defined by chromosomal anomalies such as the t(9;22) Philadelphia chromosome BCR-ABL1 or involvement of the MLL gene on chromosome 11q23. Other MPAL are divided into B/myeloid NOS, T/myeloid NOS, B/T NOS, and B/T/myeloid NOS. MPAL are usually of dire prognosis, respond variably to chemotherapy of acute lymphoblastic or acute myeloblastic type, and benefit most from rapid allogeneic hematopoietic stem cell transplantation.     

Childhood myeloid/natural killer precursor acute leukemia with novel chromosomal aberrations der(5)t(4;5)(q31;q31.3) and t(14;17)(q32;q23)

We report a unique case of childhood acute leukemia. The leukemia blasts had lymphoblastoid appearance and expressed CD33, CD13, CD34, CD4, CD7, and CD56. The morphology and immunophenotype were most consistent with myeloid/natural killer precursor acute leukemia. The blasts had a complex karyotype, including two chromosomal aberrations, der(5)t(4;5)(q31;q31.3) and t(14;17)(q32;q23), not previously described in childhood acute leukemia. The patient achieved morphological remission following myeloid-based leukemia therapy.     

Expression of NK-associated antigens in extramedullary lymph nodal blast crisis of chronic myeloid leukemia on fine-needle cytology

A case is reported of a 62-yr-old male suffering from chronic myelogenous leukemia (CML) who developed an extramedullary, para-orthic lymph-nodal blast crisis without blood or bone marrow involvement and expression of CD56/NK associated marker. The diagnosis was performed on ultrasound-guided fine-needle cytology by an immunocytochemical and flow cytometric analysis. Conventional smears showed a monomorphous population of disperse, undifferentiated cells without cytoplasm. Cells showed fragile nuclei, vesicular chromatin, and evident nucleoli. Immunocytochemistry performed on cytospin slides were negative for cytokeratin, LCA, CD20, CD45Ro, and myeloperoxidase (MPO). Flow cytometry analysis proved the myeloid origin of the tumor by expression of CD13, CD34, and CD38 and showed aberrant expression of CD56. Cytological diagnosis was confirmed by histological examination. CD56 expression is generally an expression of NK lymphoid proliferation and may be observed in acute myelogenous leukemia but has rarely been reported in CML and its related blast crisis. This unusual expression, its possible explanation, the related technical problems, and clinicopathological aspects are discussed.     

Challenge in diagnosis of CD56+ lymphoproliferative disorders: two cases of CD56+CD33+ lymphoma/leukemia

Two cases of CD56+CD33+ leukemia/lymphoma are reported. The patient in case 1 presented with skin rash, diffuse lymphadenopathy, and hepatosplenomegaly. Blasts with monocytoid and lymphoid features were present in the peripheral blood. The tumor cells expressed HLA-DR, CD4, CD33, CD38, and CD56. Cytogenetic analysis revealed del(2)(p13),del(9)(q22),add(6)(q25),add(12)(p12),-13,-18, and -20. The clinicopathologic features were similar to those of blastic natural killer cell leukemia/lymphoma or type 2 dentritic cell leukemia. The patient in case 2 presented with generalized weakness and skin erythema not responding to antibiotics. Circulating blasts with monocytoid features were seen in the peripheral blood. The tumor cells expressed CD7, CD13, CD33, CD38, and CD56, and cytogenetic analysis revealed -5,add(7)(p22),-8, del(10)(p11.2),-12,der(13; 14)(p10;p10),+14,-16,-18,-19, and del(20)(q13.1). The clinicopathologic features were consistent with a myeloid/ natural killer cell precursor acute leukemia. Both disorders are aggressive hematopoietic malignancies that have similar clinical presentation and morphology but differ in immunophenotype and cytogenetic features.