Aberrant CD2 expression in precursor-B acute lymphoblastic leukemia of childhood

Aberrant CD2 expression in childhood precursor-B ALL is rare and has recently been reported with an incidence of 3.6% in a study by Cantu-Rajnoldi et al. [Haematologica 77:384, 1992]. There was no association of the CD2 co-expression with other known prognostic factors. Our study represents the second one in the literature. Out of 60 childhood acute lymphoblastic leukemias, analyzed morphologically and by flow cytometric immunophenotyping, 49 were of precursor B origin. Of these 49 cases, CD2 co-expression was detected in 2, yielding an incidence of 4.1%. The complete immunophenotypic profiles of these two cases were as follows, respectively: (1) CD19+, CD20-, CD24+, CD10+, sig-, CD2+, CD3-, CD5-, CD7-, CD13-, CD33-, CD34+, Tdt+; and (2) CD19+, CD20-, CD24+, CD10+, sig-, CD2+, CD3-, CD5-, CD7-, CD13+, CD33-, CD34+, Tdt+. Cytogenetic analysis revealed a normal male chromosome pattern in case 1 and an abnormal female chromosome pattern [4 cells: 46, XX, del (6q) (q21 q23) and 9 cells: 46, XX, del (11q) (q14 q23)] in case 2. Both patients were in continuous complete remission at last follow-up.