Subject: What distinguishes between the different types of non hodgkins lymphoma?

I attended a science forum in London during the summer, and have grown an 
interest is cancer research. While reading up on the subject (unrelated to the 
area of science which I am currently studying) I can across a wide variation of 
the types of lymphatic cancer, what makes each of the approx. 20 types so 
unique and how does this affect the variety of treatments that should be given 
to each?

Re: What distinguishes between the different types of non hodgkins lymphoma?