Introduction

Bone marrow (BM) studies are often performed in children with solid tumors for initial diagnosis, for staging of disease, for monitoring of response to therapy, and for detecting recurrent diseases. In general, the presence of BM metastasis indicates high-stage disease and is associated with inferior outcome. Different pediatric solid tumors, however, metastasize with variable frequency depending on the tumor type. While neuroblastoma and alveolar rhabdomyosarcoma frequently present with BM metastases, other tumors such as pediatric brain tumors, non-rhabdomyosarcoma soft tissue sarcomas, and retinoblastoma metastasize less often. Some tumors, such as Wilms tumor, almost never metastasize to the BM and seldom require bone marrow evaluation. There is no single clinical finding that can predict the presence of BM metastasis in a child with a solid tumor. Bone pain, spinal cord compression, or pathologic fractures, although frequently reported, are non-specific and unreliable in confirming BM metastasis.

The standard for staging BM evaluation for solid tumors requires bilateral aspirates and biopsies with at least 1 cm of BM, not including the bone cortex or cartilage. BM biopsy may not be feasible in young infants, and a combination of MRI scans, BM aspirates, and ancillary studies may be acceptable for proper diagnosis. This approach, while sufficient for the diagnosis of metastasis, is limited in monitoring response to therapy and further follow-up. Thus, staging BM biopsy should be attempted when possible to overcome this limitation.