I found this article on the internet which explains Non-Hodgkin's Lymphoma for beginners. A sort of "Idiots Guide To NHL" sort of thing.
I have acknowledged the copyright, if this is you please contact me.
First of all, lymphoma is not a disease of the lymphatic system. It is a disease of lymphocytes, a form of white blood cells, which circulate throughout the body in the blood and lymphatic systems.
The lymphatic system and the blood system together form the circulatory >system and connect to every part of the body. Blood cells originate in the bone marrow. Lymphocytes are the "brain cells" of the immune system. They direct the actions of the other cells involved in fighting off diseases, cancers, etc. When faced with an invader, or simply a damaged cell, lymphocytes reproduce, quite rapidly in fact, and activate the other parts of the immune system.
When this occurs, these lymphocytes are called "reactive." When they've done their job, most of the newly born lymphocytes die an honourable death and things return to normal. Sometimes, however, a good lymphocyte goes bad.
It reproduces and keeps reproducing for no good reason. The newly born lymphocytes don't die an honourable death, but hang on and produce more bad lymphocytes. When this gets out of control, it is called "lymphoma."
There are many different times and places in the life cycle of a lymphocyte where things can go wrong. Depending on when and how the lymphocyte goes bad determines the particular type and grade of lymphoma. Just how widespread the bad lymphocytes are determines the stage.
If they hang around the local shop (oops, I mean a single lymph node) then it is called Stage I. If instead they rampage throughout the city (body), getting into all different kinds of places, then it might be called Stage IV.
Even in lymphoma patients, most lymphocytes are good citizens, doing their job quietly, having kids when necessary, and so on. The other kinds of white blood cells are also normal. It's just this one criminal family that's causing all the problems.
If this lymphoma mob is aggressive and keeps growing fast, then you can send out the cops (chemotherapy, radiation) to arrest (shoot on sight, actually) any lymphocyte acting aggressively. Unfortunately, any other cells that are growing quickly at the same time are subject to the same martial law. This is what causes side effects, like hair loss.
If the mob is indolent (lazy) they can't be identified as readily and the cops can't wipe all of them out. But they can do a good job of keeping them in check for many years.
Sometimes mobster lymphocytes sneak into the nursery (bone marrow) where new-born blood cells grow to maturity. This makes it easier for the mobsters' evil kin to spread. (This is called bone marrow involvement.)
Sometimes, with an aggressive mob, the cops just can't handle it. Then it's time to call out the army. They just kill everyone in the city (high dose chemotherapy.) Unfortunately this also wipes out the nursery.
Fortunately, before they bomb the place, they save enough new-borns (stem cells) to repopulate the nursery and go forth into the now empty city. If they can't get enough healthy babies from the city (the body) the powers that be find some other city (bone marrow donor) and take some of their baby cells to repopulate after the high-dose chemo. (This is called a stem cell rescue or bone marrow transplant.)
After this, the city is left with some damage, but often continues normally from then on.
(c) 1999 Robert Scott Pallack