1 National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20014
We were interested in the editorial of Clement1 which accompanied the recent article of Putnam, Moore, and Mitchell2 concerning the 19-year follow-up of patients in an epidemic of infectious lymphocytosis in 1947. Although no instance of leukemia or lymphoma was detected, the size of the study sample seemed to us too small to assess properly the risk of malignancy in these patients. To evaluate the adequacy of the sample size, we computed the expected number of cases of leukemia and lymphoma using the person years at risk of the individual cases and the 1964 U.S. mortality rates for leukemia and lymphoma.