A case of HLA-DR negative B-precursor acute lymphoblastic leukemia.

We present the case of a 9-year-old girl from northwestern Greece admitted to our Hospital because of malaise, low-grade fever, intermittent hip joint pain, anemia, leukopenia and thrombocytopenia. The examination of a bone marrow aspirate revealed the predominance of blast cells (97%) with FAB L1 morphology, immunopheno-typically positive for CD19 (95%), CD10 (95%), CD22 (95%), CD13 (82%), CD34 (95%) and CD38 (72%), with dim expression of CD45 and of the intracellular antigen terminal deoxynucleotidyl transferase (Tdt). Only 10% of the blasts expressed HLA-DR. Staining for CD2, CD3, CD5, CD7, CD20, CD23, CD33, CD14, CD15, AC133 and KOR-SA3544 was negative. Blast cells were lacking surface immunoglobulin expression and bcr/abl rearrangements were not detected. Cell cycle analysis revealed a diploid cell population. Karyotypic abnormalities were not identified. The lack of expression of HLA-DR and the presence of myeloid antigen CD13 indicated that it was a rare case of B-precursor ALL with aberrant immunophenotypic characteristics.