Histology of neuroblastoma involving bone marrow: the problem of detecting residual tumour after initiation of chemotherapy.

One hundred and eighty bone marrow trephine biopsies obtained during 68 staging procedures before and during treatment of 20 children with Stage IV neuroblastoma were reviewed. A primitive cell infiltrate with prominent fibrous stromal reaction and increased reticulin characterized the marrow at presentation. Once treatment had begun, primitive cells became difficult to find but fibrosis and a marked increase in reticulin persisted in most cases. Distortion in marrow architecture and the continuation of abnormal stromal reactions may reflect failure to eradicate tumour despite absence of detectable primitive cells. If current therapeutic options are to be assessed properly, uniformly accepted criteria to define continuance of marrow infiltration in children with neuroblastoma are needed. A scheme for classifying marrow histological appearances is presented which may prove to be of more value than a simple distinction between 'involved' and 'uninvolved'.