Cancer is a general term for any disease in which certain cells in the human body divide in an uncontrolled manner (abnormal cell proliferation). The resulting new cells may form a malignant tumor (a neoplasm) or spread throughout the body. These cells all derive from the same clone, a cancer-initiating cell that has acquired certain characteristics enabling it to divide indefinitely. The aim of this study is to contribute to the improvement of care for children with cancer in the pediatric oncology unit of the University Clinics of Lubumbashi.We conducted a retrospective cross-sectional descriptive study in the Pediatric Oncology Unit at the University Clinics of Lubumbashi during the period from January 2012 to January 2022. We included all children treated with cancer drugs in the Pediatric Oncology Unit who had a platelet count of less than 100 G/L. Most patients had developed thrombocytopenia during the 3rd cycle of chemotherapy, with a frequency of 94.87%.