Detecting CD56+/NB84+/CD45- immunophenotype in the bone marrow of patients with metastatic neuroblastoma using flow cytometry

Background: In order to identify neuroblastoma cells infiltrating the bone marrow, a triple-color flow-cytometric assay was developed combining CD56 and CD45 with the intracellular anti-NB84 specific antibody. Materials and Methods: The bilateral aspirates obtained from 27 consecutive children over the age of one year with stage 4 neuroblastoma were evaluated. Results: Neuroblastoma cells were detected in the bone marrow of 17/27 (63%) and 19/27 (70%) cases using cytomorphology and triple-color flow-cytometry, respectively. Using cytometry, the percentage of CD56+/NB84+/CD45-cells infiltrating the bone marrow ranged from 0.02% to 65%. Five out of eight patients without bone marrow involvement according to cytometry are in continuous complete remission, while only 3 out of 19 patients whose bone marrow gave positive results are still alive. Conclusion: By combining CD45 and CD56 with the specific antibody, NB84, directed against neuroblastoma cells, we developed a rapid and reliable cytometric assay that can be associated with conventional cytomorphological bone marrow evaluation to detect infiltrating neuroblastoma cells, especially in cases of dubious positivity.