Uncommon leukemic case of anaplastic large cell lymphoma diagnosed through a typical chromosomal abnormality t(2;5) with a null phenotype and aberrant expression of NG2 and CD13.

Anaplastic large cell lymphoma represents approximately 10-15 % of pediatric non-Hodgkin lymphomas. Leukemic presentation is very rare, and in particular, the null phenotype ALCL without typical anaplastic morphology together with aberrant expression of CD13 and/or CD11b represents a diagnostic challenge. We report a case of a 9 year-old boy with leukemic presentation of ALCL with the typical translocation t(2;5)(p23;q35); in this patient, the only positive antigens identified by immunophenotyping were CD13, NG2 HLA-DR, and CD38. To our knowledge, aberrant expression of NG2 has never been reported in ALCL cases (Tab. 1, Fig. 6, Ref. 20).