GENERAL CONSIDERATIONS 



In a hyperplasia, as opposed to a neoplastic condition, the 

 proliferation is not unlimited in any one site, however 

 prolonged the stimulus, and there is a considerable con- 

 stancy of cytological response in relation to the stimulating 

 agent. 



Neoplastic conditions, on the other hand, rarely show local 

 and limited cellular proliferation, and grade into conditions 

 showing all the typical features of malignancy : invasion of 

 adjacent normal tissues and abnormal cytological appear- 

 ances, including atypical mitoses. It is, however, particularly 

 characteristic of the group of reticuloses that there are many 

 conditions in which, although cell proliferation is progressive 

 and leads inevitably to death of the subject, the gross features 

 of malignant disease are lacking or appear only as an irregu- 

 lar terminal event. Hodgkin's disease, follicular lymphoma 

 and chronic lymphatic leukaemia are clearly not mahgnant 

 conditions in any ordinary sense. Equally there is no evidence 

 that they have a micro-organismal cause. There is every- 

 thing to be said for the contention by Marshall (1956) that 

 they represent conditioned neoplasms in the sense of Furth 

 (1953, 1954), that is, they are still under partial control of 

 hormones or other normal controlling agents. 



Every cell in the body is played on by controls which 

 ensure that the number and disposition of any type is in a 

 reasonable relationship to the current needs of the body, 

 whether these are physiological or represent evolutionarily 

 significant impacts of trauma or infectious disease. The 

 number of lymphocytes in the blood fluctuates only within 

 narrow limits, despite the enormous numbers poured in 

 from the thoracic duct. The lymph nodes in health remain 

 approximately uniform in size and internal architecture. 

 Although the controls which maintain this homeostasis are 

 by no means fully understood, it is clear enough that they 

 exist. There is a widespread opinion, which is rather difficult 

 to prove or disprove, that, on the whole, control of somatic 

 cells is essentially a matter of holding in leash tendencies of 



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