Epidermal Carcinogenesis in Young and Aging Animals

Spontaneous epidermal carcinomas show an age (t) related incidence (I) conforming to the following expression: $$ \textup{I}=\textup{ct}^{\textup{b}} $$ (c and b are constants) (1). As an explanation of these age incidence curves, the local multistep mutation hypothesis (2) is widely, but not universally, accepted.