Acute Myeloid Leukemia with Coexpression of Lymphoid-Associated Antigens: Clinicobiological Associations and Prognostic Implications,

Abstract 3596 Immune phenotyping plays a critical role in the diagnosis and classification of acute leukemia. Several studies have reported a variable proportion of patients with acute myeloid leukemia (AML) expressing lymphoid-associated antigens (LAA). The exact frequency and true clinical significance of this phenomenon remains undefined due to inconsistencies between series, likely related to methodological aspects or potential case selection biases. We retrospectively evaluated the expression of LAA in blast cells from 278 consecutive and unselected patients with AML diagnosed in our Department between 2002 and 2010. The patient cohort included 168 males and 110 females with a median age of 61 years (range, 10–88); 146/278 cases were above the age of 60. Within this cohort, 190 cases (68%) had de novo AML, whereas the remaining 88 cases (32%) concerned secondary AML (sAML) to either MDS (n=80) or other non-hematologic malignancies (n=8). Patients were treated uniformly according to age with Aracytin/Idarubicin induction regimens (“3+7” or “2+5” for ages \q60 or ≥60, respectively). The immunophenotype was determined by flow cytometric analysis of (mainly) bone marrow aspirate and/or peripheral blood samples utilizing a primary CD45/side scatter (SSC) gating procedure with antibodies against CD7, CD13, CD19, CD33, CD4, CD10, CD34, CD117, CD64, HLA-DR, CD20, CD2, CD15, CD56, CD14, CD8, MPO, CD3, CD79a, CD22, TdT and lysozyme; a cut-off value for positivity of 20% was adopted. Overall, we identified 153/278 cases (55%) expressing at least one LAA. The most commonly expressed LAAs were CD4 (outside AML with monocytic differentiation), CD56, CD7, CD2, CD10 and CD79a (in 39%, 33%, 29%, 14%, 10% and 8% of LAA+ AML cases, respectively); interestingly, all CD79a-positive cases co-expressed at least one more LAA. A significant association was identified between LAA expression and cytogenetic profile: in particular, at least one LAA was detected in 37/50 cases (74%) with adverse cytogenetics (SWOG unfavorable and/or monosomal karyotype), compared to 24/41 (58%) cytogenetically favorable cases and 68/134 (51%) cytogenetically intermediate risk cases (p=0.01). No other statistically significant associations were found for LAA expression (positive vs. negative) in respect to age and complete remission (CR) rate. Furthermore, the frequency of LAA-positive cases was identical (55%) in both de novo AML (105/190 cases) and sAML (48/88 cases). Monoparametric statistical analysis was also performed individually for each of the six more frequent LAAs. Significant associations (p Disclosures: No relevant conflicts of interest to declare.