Flow Cytometric Phenotype of Rhabdomyosarcoma Bone Marrow Metastatic Cells and its Implication in Differential Diagnosis with Neuroblastoma

Abstract

Background: The goal of this study was to develop a flow cytometric (FCM) method for assessing the presence of metastatic cells in bone marrow (BM) and peripheral blood (PB) obtained from rhabdomysarcoma (RMS) patients. Myogenin (Myf4), a specific molecular RMS marker, was also investigated in the same samples. Since neuroblastoma (NB) metastasizes to the BM, the potential application of cytometry in differential diagnosis was explored. Patients and Methods: CD45, CD56, CD90 and CD57 antibodies were used in 7 paired BM and PB samples (from 7 RMS stage IV patients at presentation), 23 BM samples (from 13 RMS stage I and II patients at presentation), and ten paired BM and PB samples taken at presentation and five BM samples taken at recurrence from 13 NB stage 4 patients. Results: All seven BM samples from RMS stage IV (but not those from patients with localized disease) showed both the CD45-CD56+ phenotype and the Myf4 transcript. Four cases also showed CD90 and two CD57 positivity. Neither the CD45-CD56+ phenotype, nor Myf4 were recorded in the BM and PB samples from patients with localized disease. All the NB BM samples (15/15) showed the CD45-CD56+ CD90+ phenotype and 10/15 also showed CD57 positivity. Only 3/10 blood samples from the NB patients revealed tumor cells. Conclusion: CD45, CD56, CD90 and CD57 antibodies can be used in FCM for marrow metastasis detection in both, RMS and NB patients.