Abstract
The bottom line here is how or whether our toxicological studies relate to ourselves, to human neoplasia—but the latter is, in important ways, imperfectly defined by the best that can so far be arranged using morphological and epidemiologic methods. There are at least three basic questons: 1) with what precision can the histopathologist define and diagnose cancer in humans—hence emphasis here upon human cancer models, 2) to what extents can difficulties be resolved using animal models, where some similar difficulties are met, and 3) to what extents can epidemiology resolve these difficulties. Not all these problems can be resolved, and the investigator is left with a residue of questions for which no answers are presently available. Some of these are exemplified or precipitated by inconclusive or mistaken diagnoses.
In the future awaits practical help from specific biochemical markers and morphometry, but in the present, vigilance and consultation should limit error to a small fraction of observations. In the meantime, existing methods and data are perfectly adequate for study and action in various clinical problems, eg. transmission of familial polyposis of colon, definition and control of various adverse drug reactions.