Burkitt's leukemia with an atypical immunophenotype: report of a case and review of literature.

Burkitt's leukemia (BL) constitutes a small but important fraction of acute leukemias in children. It is an aggressive type of leukemia that is responsive to high-intensity, short-duration chemotherapy with complete remission possible in 75% to 90% of cases. The recognition and proper designation of BL is important because treatment differs from that of precursor B-cell acute lymphoblastic leukemia (pre-B ALL). Burkitt's leukemia is separated by its typical morphologic features (blasts with typical French-American-British [FAB] L-3 morphology compared to FAB L-1/L-2 morphology in pre-B ALL) and a classic immunophenotype (blast positivity for CD45 [bright], CD20 [bright], CD10, CD19, surface immunoglobulin [SIg], Ig light chain restriction, and negative terminal deoxynucleotidyl transferase [TdT]) compared to pre-B ALL blasts (which are positive for CD45 [dim], CD10, CD19, and TdT and negative for CD20 and SIg). The diagnosis of Burkitt's leukemia is confirmed by the characteristic cytogenetic findings.The combination of Burkitt's morphology with precursor B-cell immunophenotype may present a diagnostic pitfall, resulting in delay of proper management.We describe such an atypical case in a 12-year-old girl and emphasize that correct classification and treatment starts with proper morphologic/immunophenotypic correlation, and the awareness of the overlapping features in some cases.