Original Article Ana Paula Alegretti¹ Christina Matzenbacher Bittar² Rosane Bittencourt² Amanda Kirchner Piccoli¹ Laiana Schneider³ Lúcia Mariano Silla² Suzane Dal Bó¹ Ricardo Machado Xavier4 1Clinical Pathology Service, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul – UFRGS, Porto Alegre, RS, Brazil ²Hematology and Bone Marrow Transplantation Service, Universidade Federal do Rio Grande do Sul – UFRGS, Porto Alegre, RS, Brazil ³Universidade Federal de Ciências da Saúde de Porto Alegre, RS, Brazil 4Rheumatology Service, Hospital das Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul - UFRGS, Porto Alegre, RS, Brazil. Conflict-of-interest disclosure: The authors declare no competing financial interest Submitted: 11/16/2010 Accepted: 3/22/2011 Corresponding author: Ana Paula Alegretti Hospital de Clínicas de Porto Alegre Universidade Federal do Rio Grande do Sul – UFRGS Ramiro Barcelos, 2350, 2º andar 90035-903 – Porto Alegre, RS, Brazil Phone: 55 51 3359-8316 anaalegretti@gmail.com www.rbhh.org or www.scielo.br/rbhh DOI: 10.5581/1516-8484.20110054 202 The expression of CD56 antigen is associated with poor prognosis in patients with acute myeloid leukemia Background: The expression of CD56 is considered a bad prognostic factor for overall survival, lower rates or short complete remission and extramedullary invasion but the results are controversial. The importance of validating new prognostic parameters in acute leukemias was the reason to investigate the CD56 expression in blast cells of patients with acute myeloid leukemia. Methods: A cohort of 48 patients treated at Hospital de Clinicas de Porto Alegre and diagnosed with acute myeloid leukemia as classified by the French-American-British group (FAB) criteria using cell morphology, cytochemistry and flow cytometry were evaluated. Results: Eight cases (16.7%) were CD56 positive without correlation to age or gender. The highest incidence of CD56 positivity was in FAB subtypes M4 and M5. The death rate during induction was not significantly different between patients with and without CD56 expression (62.5% vs. 27.5%; p-value = 0.097). However, patients that expressed CD56 had significantly lower overall survival than those who did not (mean 4.0 months vs. 14.5 months; p-value = 0.03). Conclusions: The data suggest that expression of CD56 in acute myeloid leukemia may be indicative of poor prognosis because it is associated with a shorter overall survival. The death rate during induction was not significantly different despite an apparent difference in proportions between groups. Keywords: Antigens, CD56; Leukemia, Myeloid; Prognosis Introduction Acute myeloid leukemia (AML) is a clonal malignant disease of the hematopoietic tissue. Its estimated incidence is 30% of all adult leukemia; the relative survival time for adults diagnosed between 1990 and 1994 was one year in 34% of cases and five years in 15%.(1) The commonly used method to classify the various subtypes of AML was developed in 1976 by the French-American-British (FAB) cooperative group, based on morphologic and cytochemical aspects.(2) Immunophenotypic methods were later incorporated as part of the diagnostic criteria. Conventional morphology supplemented by cytochemistry is often sufficient to differentiate leukemia types. Occasionally, myeloblasts have atypical, agranular lymphoblast morphology, which may impair diagnosis.(3) Cases such as minimally differentiated AML (FAB M0), acute erythroid leukemia (FAB M6) or acute megakaryoblastic leukemia (FAB M7) require complementary immunophenotyping.(1) Immunophenotyping is widely used and complementary to morphological, cytochemical and karyotypic (cytogenetics) studies, allowing a more precise diagnosis and classification of AML.(4) The assessment of membrane or intracellular antigens (cluster differentiation – CD) using flow cytometry (FC) has enabled the identification of immunophenotypic peculiarities of cells. Distinctive characteristics have been studied for their possible prognostic value(5,6) in predicting response to treatment, rate and duration of complete remission (CR), disease-free survival, overall survival (OS) and potential of extramedullary invasion (EMI), as well as the correlation of molecular expression with cell resistance mechanisms or apoptosis-regulating proteins.(7) The use of these expressions was proposed to monitor minimal residual disease (MRD)(8) and more recently to develop and monitor antibody-based treatment strategies.(9) CD56 is commonly expressed in natural killer cytotoxic lymphocytes (NK cells) and in other lymphocyte(10) and monocyte(11) subtypes. CD56 NK cells are an important cell component of the innate immune system as they are the major source of IFNg (interferon- gamma). Normal plasmocytes are CD56-negative and when present, this expression has been used to distinguish multiple myeloma (MM) from monoclonal gammopathies of undetermined significance or reactive plasmocytes.(12) CD56 can also be expressed in Rev Bras Hematol Hemoter. 2011;33(3):202-6