Lucy's doctor explained this to us when she was diagnosed, but until then I didn't know the difference between Hodgkin's and non-Hodgkin's lymphoma. Lemme break it down for ya...
Basically, there are two different kinds of lymphoma, which in case you're totally unaware is cancer affecting the lymph nodes. The two kinds are known as Hodgkin's Disease (or Hodgkin Lymphoma) and Non-Hodgkin's Lymphoma. The diseases are pretty similar in that they both involved rapid cell growth in the lymphatic system of our bodies, but with Hodgkin's disease there is a presence of a Reed-Sternberg cell (see image below).
Reed-Sternberg cells determine whether a patient has Hodgkin's or Non-Hodgkin's lymphoma.
The scientists who isolated the Reed-Sternberg cell were able to tell Hodgkin's from non-Hodgkin's. Hodgkin's Disease usually affects younger people, but it's pretty rare (about 8,000 cases per year). Non-Hodgkin lymphoma, which is what my sister Lucy has, is much more common (about 65,000 cases per year). Both Hodgkin's and Non-Hodgkin's have many of the same symptoms, which can be anything from enlarged lymph node(s), weight loss, fevers, and night sweats. Weird tidbit: a symptom of Hodgkin's Disease is itching and pain when drinking alcohol.
The treatments for both Hodgkin's and non-Hodgkin's are similar, usually involving chemotherapy, radiation and drugs. The diseases will kill you if you don't treat them, but the good news is both enjoy pretty good rates of cure.
Anyway, that's the difference in a nutshell.