Although childhood cancer remains the leading cause of disease-related deaths among children younger than 14 years of age, it is relatively rare. ^{Endnote 1 , Endnote 2} Each year, an average of 910 children are diagnosed with cancer in Canada, and 139 children die of the disease. ^{Endnote 3} Cancers in children differ biologically from those usually found in adults. ^{Endnote 4 , Endnote 5} The majority of cancers in adults are carcinomas of the epithelial tissues that line organs such as the breast, lung, colon and prostate. In children, carcinomas are rare and childhood tumours are more likely to be embryonic or hematopoietic in origin. ^{Endnote 5} Leukemias, lymphomas and central nervous system cancers represent the largest diagnostic groups. ^{Endnote 5} Compared to cancers in adults, cancers in children have shorter latency periods and are generally more aggressive, invasive and advanced at diagnosis. ^{Endnote 5}