New medical modelling indicates nearly half of children with cancer are never diagnosed and may die untreated including those in the Pacific Islands, Africa and South Central Asia.
By contrast, in North America and Europe only three per cent of cases remain undiagnosed.
A study published in the Lancet Oncology reports that by 2030 around 2.9 million childhood cancer cases will be missed if health systems don't improve.
Accurate estimates of childhood cancer incidence are critical for policy makers to help set healthcare priorities and plan for effective diagnosis and treatment of all children with cancer, according to one of the study's authors, Zachary Ward from the Harvard T.H. Chan School of Public Health.
He said under-diagnosis had been acknowledged as a problem and the new model provided specific estimates that had been lacking.