A malignant tumor that occurs in children. Representative examples include soft tissue and bone sarcomas (e.g. osteosarcoma) and embryonal neoplasms (e.g. hepatoblastoma and rhabdoid tumor). The disease is childhood malignant neoplasm (MONDO_0006517). Also known as: childhood cancer, childhood neoplasm, malignant, malignant childhood neoplasm, malignant childhood tumor, malignant childhood tumour, malignant paediatric neoplasm, malignant paediatric tumour, malignant pediatric neoplasm.