4 Features Age at diagnosis (y) Median Range <1 1–10 >10 Gender M F Sex ratio (M/F) FAB subtype n (%) L1 L2 NS Median Range <50 >50 CNS disease∗∗ Mediastinum∗∗ Leukocyte count (×109/L) International Journal of Pediatrics Table 2: Patients’ characteristics. All patients (n = 275) T-cell ALL (n = 59) pB-cell ALL (n = 216) P-value 7 0.5–17 6 (2.18%) 184 (66.91%) 85 (39.91%) 161 (58.55%) 114 (41.45%) 1.41 : 1 144 (52.36%) 101 (36.73%) 30 (10.91%) 20.14 1–830 178 (94.96%) 96 (35.05%) 4/218 (1.83%) 35/218 (16.05%) 9 0.5–17 1 (1.69%) 32 (54.24%) 26 (44.07%) 44 (57.63%) 15 (25.42%) 2.93 : 1 34 (57.63%) 22 (37.23%) 3 (5.08%) 116 1.5–718 16 (27.12%) 43 (72.88%) 2/45 (4.44%) 28/45 (62.22%) 6 0.5–17 5 (2.31%) 152 (70.37%) 59 (27.31%) 117 (54.17%) 99 (45.83%) 1.18 : 1 110 (50.93%) 79 (36.57%) 27 (12.50%) 11.38 1–830 162 (75.35%) 53 (24.65%) 2/173 (1.16%) 7/173 (4.05%) .048‡ .008‡ .85 <.0001‡ .42 <.0001‡ ALL: acute lymphoblastique leukaemia, F: female, M: male, Y: year, CNS: central nervous system, NS: not speciﬁed. ∗Mature B-cell ALL excluded. ∗∗Cases with completed data. ‡P ≤ .05 (statistically signiﬁcant). The relative frequencies of immunological subtypes in this study are very similar to that reported by the developed countries of Europe and USA, except for the higher frequency of T-ALL (21.15%) [15–19]. One study carried out on 100 Moroccan paediatric patients showed a diﬀerence in the incidence of T-ALL [20]; the relative incidence of T- ALL is decreasing from 38% to 21%. The absence at that time of a system of immunophenotyping referrals and the small number of cases analyzed, could explain the diﬀerence in T-ALL incidence observed. In the present study we took advantage of the recent strategy of Acute Leukemia diagnosis in Morocco. Importantly, the frequency of T-ALL observed did not diﬀer signiﬁcantly when we include the cases diagnosed after the study period. As it has been described in children [9, 14], the majority of cases were from pB-ALL (78.5%) with the dominance of early pre-B phenotype (69% of pB-ALL), followed by pre- B in 27.6% and Transitional pre-B in 3.4%, with typical peak between 3 and 5 year. The signiﬁcantly higher incidence of CD10+ pB-ALL (197/275, 71.6%) observed was like that observed in developed centers [14, 21, 22]. In T- cell ALL subgroup, with 80.4%, there is an excess of the common thymocyte subtype displaying reactivity with CD1a as compared with the frequency reported by others [9, 14, 23, 24]. We conﬁrmed the close association between T-cell phe- notype with older age, male gender, mediastinal mass, and higher leukocyte count [1, 2, 14]. Data concerning the antigen expression for each class of ALL showed as has been reported in children in various developing and developed countries [9, 21, 24–27], every case of B cell lineage ALL expressed CD19, CD22, and CD79a. Cytoplasmic CD3, CD5, and CD7 were the most sensitive antigens for the T-cell lineage ALL. However, the results of the detailed immunologic markers analysis, underline some diﬀerence of pattern of immunologic marker expression of T-cell ALL. They show that frequencies of CD1a, surface CD3, and CD4 are higher than generally observed (less than 45%) [9], and the expression of TdT is observed in fewer cases (70.5%) than reported in previous studies, more than 90% [9, 24]. CD10 expression was detected in 197 cases (91.2%) of the 216 pB-ALL cases and in 10 T-ALL cases (21.3%) of the 47 cases tested for this antigen. Cases of pB-ALL having the CD10 expression had lower leukocyte count and the majority of cases (141/216) were between 1 to 10 years of age (P not signiﬁcant). CD10+ T-ALL cases were characterized by lower leucocytes count in female sex (P not signiﬁcant) and older age. Studies of the prognostic signiﬁcance of CD10 expression in ALL have