Neoplastia Diseases in Infants and Children* EDWINA. LAWRENCEANDEUGENEJ. DONLAN

The predominant malignant neoplasms of in fants and children arise from tissues of mesenchymal origin, in contrast to the characteristic epithelial malignant tumors of adults. A sound ex planation for this apparent influence of age on tumor types would be a significant contribution to oncology. It has been suggested that age alone has little effect on the development of sarcomas and that the incidence of sarcomas varies only slightly from age 15 to age 75, if percentage corrections are made on the proportionate number of persons liv ing in various age periods (21). However, age is definitely important in the development of car cinomas. They are rare in infancy and childhood, begin to be prominent aberrant growths in late youth and early adult years, and reach their peak of frequency in the middle decades of life. Their increasing incidence with age supports the con cepts of carcinogenesis in the human that were so ably presented by Cramer (4). If one accepts the ramifications of his theories and recognizes the im portance of the time element in carcinogenesis, it is not difficult to understand why carcinomas are not prominent neoplasms in the first decade of life. Explanations for the origin of human carcino mas have not proved adequate for the origin of the sarcomas. Even though the belief that childhood tumors arise from embryonal rests continues to receive support (1, 12), it is not inconceivable that an influence on mesenchyme in intra-uterine life is equally important, thus explaining the greater numbers of malignant tumors reported in the first 5 years of life than in the subsequent two 5-year periods. On the other hand, if the incidence of sar coma does not vary significantly in later age pe riods as has been stated, it is difficult to under stand how the effects of an adverse intra-uterine milieu could be delayed until late adult life. Our limited knowledge of the methods of origin of malignant neoplasms of infants and children may be due in part to their rarity. Farber (10) has stated that the 301 histologically verified malig nant tumors, excluding the leukemias, studied dur-