Chapter 3 discusses cancer diagnosis, risk stratification, and therapeutic choices in children and young people. Radiological investigations support the diagnosis and provide staging information for accurate risk stratification. Interventional radiology is useful for obtaining tissue for pathological examination. Histopathology and molecular studies define the precise tumour type and subtype and are used to confirm or rule out the presence of metastatic disease. Post-operative histopathology defines the extent of spread and is important for the staging of some tumours. Together, these findings inform multidisciplinary team discussion and help to identify the best treatment schedule. A significant proportion of cancers have a genetic basis, and it is important to identify these from the family history, predisposing syndromes, or tumour type. Modern molecular genomic techniques have made definitive diagnosis easier. Some genetic conditions lead to increased radiosensitivity and may predispose the patient to excessive radiation-related morbidity and a high risk of second primary tumours.
