Bone marrow invasion in pediatric solid tumors is an essential area of research, as it has a significant impact on prognosis and treatment strategies. Bone marrow metastases occur when non-hematopoietic malignant cells infiltrate the bone marrow, often leading to severe hematological disorders and high mortality rates if not identified early. The mechanisms of bone marrow invasion involve tumor cells escaping into the bone marrow, forming micrometastases which can then take on aggressive forms. Bilateral bone marrow aspirates and trephine biopsies (BMAT) are essential for accurate classification, as discrepancies in results can occur. In addition to their progressive nature, pediatric solid tumors are characterized by a high metastatic potential, particularly in the bone marrow. This retrospective study analyzes a series of 52 cases of solid tumors with bone marrow invasion, diagnosed in the hematology laboratory and pediatric hemato-oncology unit (UHOP) of the Hassan II University Hospital in Fez over a six-year period, from January 2016 to December2022. Evaluation of bone marrow involvement is a key factor in therapeutic orientation and assessment of response to treatment. The presence of bone marrow metastases is associated with a poor prognosis. The haematology-biology laboratory plays an essential role in detecting extra-haematopoietic cells suggestive of bone marrow metastases, over and above standard tests. Despite advances in our understanding of spinal cord metastases, challenges remain in early detection and effective treatment, necessitating ongoing research to improve outcomes for affected children. In this article, we review the epidemiology, molecular mechanisms, clinical diagnosis, treatment and prognosis of bone marrow invasion in solid tumors in the pediatric population.