Aging and neoplastic progression.

Aging is the gradual development of individuals of a particular species in time. Interspecies comparison shows the variability of the aging processes in ontogeny which is species-specifically fixed. e.g. a mouse will never be able to reach the life expectancy of a blue whale or man. Certain changes of the life span have been observed in aging human populations, on an individual basis, or in zoo animals under the care of veterinarians. Cells of different tissues exhibit a varying senescence additionally influenced by concomitant diseases. The age spectrum of neoplasms cannot be simplified. It is misleading to state that neoplasms are diseases of the elderly because this is the case only in certain, very common neoplastic diseases, such as colon cancers, but not regarding pediatric neoplasms as retinoblastoma, nephroblastoma, or Ewing sarcoma, and osteosarcoma in the young. This paper evaluates the diversified age changes in the development of selected neoplastic diseases.