To the Editor.
—We would like to add a postscript to the discussion on the benign nature of neonatal cancer.1 It may be that acute lymphoblastic leukemia can be added to the list of diseases mentioned. This disease is distinctly uncommon in infants under 1 year, accounting for less than 10% of all cases. The incidence then rises steeply to a peak at 3 years. This pattern is not seen in the rare childhood cases of acute myeloblastic leukemia where there is no particular age distribution.Court Brown and Doll2 postulated that the peak was due to a latent period required for some unknown etiologic agent to exert its full effect. It may be, however, that passive immunologic factors keep the disease at bay in early life.Supporting evidence for this concept grows: in Burkitt lymphoma the period of protection extends for a longer time than in other