Having cancer at any age is a shock, but it is never worse than when found in a child. Among Japan's roughly 20m kids under the age of 15, about 1,600 of them have the most common form of cancer in children -- Leukemia. Of the various types of this blood disease, approximately 80% have Acute Lymphoblastic Leukemia (ALL) and 20% Acute Myelocytic Leukemia (AML).