Although the terms premalignant and precancerous leave much to be desired since they imply a degree of predictability and a magnitude of risk seldom supported by the facts, considerable prominence is given to them because they may afford the physician a unique opportunity for true cancer prevention. In general, the terms premalignant and precancerous are applied to those benign lesions or conditions which, although innocuous in themselves, may predispose the person harboring them to subsequent development of cancer. This may occur by means of so-called "malignant degeneration" of benign lesions or by the development of cancer near by, suggesting an organwide physiologic or pathologic abnormality which predisposes the person to both the premalignant and the malignant lesions. Such a definition excludes those lesions which, when first encountered, may actually be malignant but are indistinguishable clinically from their benign counterparts.

Although this is a controversial area of cancer knowledge, we believe that premalignant lesions should be removed or otherwise treated (in certain cases, periodically observed) for the following reasons:

1. Although the risk of cancer eventually developing from premalignant lesions may range from very slight to very great in a large series of patients, there is no reliable way of looking into the future and distinguishing the good prognosis from the bad in the individual patient.

2. Often it is impossible to distinguish a benign but premalignant lesion from a genuine cancer without accomplishing removal-or at least biopsy.

Conclusion

The most important factors in effective cancer control today, at the individual or community level, are the doctor in his office and the patient-both not merely content to rule out cancer at the first signs or symptoms of the disease (early diagnosis) but motivated beyond that to look for its earliest be-ginnings by means of a periodic general check-up in the presence of apparent good health (cancer detection).

It is our firm conviction, supported by studies now in progress at Strang Clinic, that many lives presently lost can be saved as a result of an acquaintance with, and application of, the practical techniques of cancer detection, diagnosis, and prevention described in this book.