However, no clear distinction was possible between normal residual BM MSC and non-hematopoietic neoplastic cells in BM samples infiltrated by other types of cancer, such as rhabdomyosarcoma; this might lead to a lower sensitivity of detection of minimal numbers of CD45− CD56+ non-hematopoietic tumor cells in BM in this subgroup of patients. The gene discussed is NCAM1; the disease is rhabdomyosarcoma.