2l8 C. p. RHOADS 



that the neoplastic cell possesses special privilege and a profound bio- 

 logical advantage over its normal fellows. It apparently can carry out 

 unusual reactions as shown by its abilities to invade, distort, and destroy 

 normal tissue, to survive in the midst of violent inflammatory reactions, 

 and to withstand invasion by microorganisms. It goes its own way — it 

 has the property of autonomy and in many instances something more. 



A simple quantitative increase in the rate of growth of cells, associ- 

 ated with a decrease in their ability to differentiate, sometimes has been 

 advanced as a generalization sufficient to explain the unique properties 

 of neoplastic tissue. It is desirable to establish at the outset how sound 

 this view is, to decide whether it is sufficiently inclusive to comply with 

 all of the facts, and to ascertain to what extent it can be used as a basis 

 for planning new experiments, more conclusive than the ones now at 

 hand. 



The fact that some cancer cells multiply rapidly is proved by measure- 

 ment of their metabolic processes. Rapid growth is not a distinctive 

 quality, however, since certain normal cells, devoid of autonomy, multi- 

 ply even more rapidly, as shown by Brues (2). The evidence for the 

 limited differentiation of cancer cells is adequate, but also, like rapid 

 growth, not uniformly present. In some instances, certainly, little evi- 

 dence for the existence of any normal function can be detected, and in 

 essentially all, the cellular activities seem to be less specialized than are 

 those of normal cells of similar types. In the vast majority of neoplasms, 

 however, some evidence of differentiated form and function is at hand 

 and it may be very impressive. Hyperthyroidism due to functioning 

 thyroid carcinoma in the absence of the thyroid gland (3) and the pro- 

 duction of hormones by tumors of other endocrine organs provide satis- 

 factory proof that highly specialized activities may continue even though 

 the cells responsible for them clearly possess wholly abnormal malignant 

 qualities of invasiveness and destructiveness. Clearly, something more 

 than a quantitative change in the rates of growth and differentiation is 

 required to convey the property of neoplastic growth. 



The analogy is frequently drawn between cancer and embryonic cells 

 on the grounds that both grow rapidly and are little differentiated. The 

 embryonic cell certainly is not a neoplastic structure, however, nor is it 

 likely to become one without very considerable alteration. It has no au- 

 tonomy and lives dependent upon its associates. The cancer cell is far 

 more competent, aggressive, and malignant, and less susceptible to nor- 

 mal control and to orderly differentiation than is its normal embryonic 



