We present the incidence and the immunologic characteristics of acute lymphoblastic leukemia (ALL) subsets in Moroccan children. We studied 279 unselected patients below the age of 18 years with newly diagnosed ALL. Cases were classified according to immunophenotype: 216 (77.42%) precursor B-cell phenotype (pB-cell), mature B-cell in 4 (1.43%), and T-cell in 59 (21.15%) cases. The subclassification using the CD10 antibody revealed 197 cases pB-ALL CD10+ (91.2%) and 9 cases T-ALL CD10+ (19.2%). The age distribution showed a peak in incidence between 3 and 5 years among the pB-cell ALLs subtype. There was a significantly higher frequency of males in the T-ALL subset (M/F ratio: 2.93 : 1) and more females in the T-ALL CD10+ subset when compared with the T-ALL CD10– subset. All tested pB-cell-lineage ALLs expressed CD19, CD79a, and surface CD22, terminal deoxynucleotidyl transferase (TdT) was detectable in 89.9% of cases, and cells in 74.1% of cases express CD34. All tested T-lineage ALL cells have surface CD7 and cytoplasmic CD3 (cCD3) antigens, CD5 was found in 98.2% cases, and 70.5% express TdT. CD1a, surface CD3 (sCD3), and CD4 are detected in more than 80% of cases; this frequency is higher than the 45% generally observed. Myeloid antigens occur more frequently and were expressed in 124 (57.4%) of pB-cell-ALL cases and 20 (33.9%) of T-cell ALL cases. Our results show that the distribution of ALLs in Moroccan children is similar with the general distribution pattern in developed countries except for the high frequency of T-ALL phenotype. The phenotypic profiles of our patients are close to those reported in literature for B-lineage ALLs; for the T-cell ALL subgroup, the blast cells express more CD1a, surface CD3, and CD4 while expressing less TdT. The high frequency of CD1a expression resulted in an excess of the common thymocyte subtype.

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Mixed phenotype acute leukemia (MPAL) includes biphenotypic and bilineal types of leukemia, which constitute rare subtypes that require individualized therapy. Outcomes in Moroccan patients with MPAL are unknown. Among 1264 patients with acute leukemia, 20 were classified as having MPAL, including 17 with biphenotypic acute leukemia (1.3%) and 3 with bilineal leukemia (0.2%). There were 8 adults and 12 children. In 12 cases (60%), leukemic blasts expressed myeloid and T-lymphoid antigens, and, in 5 cases (25%), leukemic blasts expressed B lymphoid antigens plus myeloid antigens. Patients were initially treated on protocols for acute myeloid leukemia (n=4), acute lymphoblastic leukemia (ALL, n=14), or with palliative care (n=2). The probability of survival at 2 years in MPAL cases was 52%± 14%. Six of the 12 patients younger than 15 years remain alive versus 1 of 8 adult patients. Patients treated with ALL-directed therapy had significantly higher overall survival than those treated with acute myeloid leukemia-directed therapy (P=0.003). There was no association between the phenotypic characteristics and the clinical outcome (P=0.83). In conclusion, MPAL represents 1.5% of acute leukemia in Morocco. The prognosis is poor, but initial treatment with therapy directed toward ALL, improved supportive care, and the prevention of abandonment of therapy may improve outcomes in this subgroup of patients.

Background: There is paucity of detailed studies of adult T cell acute lymphoblastic leukemia (T-ALL) in developing countries reflecting the condition of these patients including clinical and biological features. Objective: This study was carried out to analyze the immunophenotypic characteristics of 40 Moroccan patients with T-ALL and its association with biological and clinical features. Patients and Methods: Between 2006 and 2009, 130 adult patients diagnosed with acute lymphoblastic leukemia (ALL) were immunophenotyped by 3-color flow cytometry using a panel of monoclonal antibodies. Cases presenting features of a T-lineage phenotype were subjected to detailed analysis including immunophenotypic, clinical and biological parameters. Results: Proportion of T-ALL among ALL Moroccan patients was 31.0%. Median age of patients was 28 years. Twenty-nine patients were females and 11 were males. 45.0% of patients (18/40) had features of immature T-ALL stages (pro-T and pre-T ALL), 30.0% (12/40) of CD1a+ cortical T-ALL stage and 25.0% (10/40) had a characteristic phenotype of medullary T-ALL. The frequencies of progenitor cell markers CD10, CD34 and TdT expression were 14.0; 57.5% and 50.0% respectively. The aberrant expression of B lineage associated antigen CD79a were positive in 20.5% of the cases and the aberrant expression of myeloid antigens CD13 and/ or CD33 was found in 22 (55.0%) cases. No significant association was encountered between TdT, CD34 or myeloid antigens positivity and high risk features at presentation as age, sex, and white blood cells. However, myeloid antigens (CD13 and/or CD33) was significantly associated with T-cell maturation stages (p = 0.009). Conclusion: To the best of our knowledge, this is the first report from North Africa of immunophenotypic study on adult T-ALL. Our findings indicate that the proportion of T-ALL among ALL in Morocco is similar to that reported in others Mediterranean countries like France and Italy and that myeloid-associated antigens expression is frequently associated with immature immunophenotype.

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