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Cancer is rare in childhood (an estimated 9,510 cases occur in the United States each year), but it is still a
leading cause of death in this age group in developed countries.
Acute leukemia is the most common form of cancer for children in most countries, especially in early childhood.
In tropical Africa, lymphomas are more common. Brain tumors generally account for one-fifth to one-fourth of childhood
cancers. Carcinomas, the common epithelial cancers of adults, are rare in children. Sarcomas of bones and soft tissue
are much more common, accounting for more than 10 percent of cancers, compared with less than 2 percent in adults.
Hereditary cancer syndromes account for the occurrence of several types of childhood cancer (especially retinoblastoma
and Wilms tumor). A few environmental exposures have been identified as risk factors, mostly related to infectious agents.
These are responsible for the frequency of Kaposi sarcoma and Burkitt lymphoma in Africa, for example.
There has been an increase in the incidence of childhood cancer in the United States and in Europe since the 1970s, although
this may have ceased since the 1990s. However, this has been accompanied by great improvements in the treatment
of childhood cancers, with resultant benefits in terms of survival. Mortality from cancer in childhood is therefore falling in the developed world.
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