The word tumor is --or was-- a Latin word meaning swollen or enlarged. People used to talk about the tumor of pregnancy, or the tumor of infection or inflammation. The word tumor has been converted to a noun meaning an abnormal growth, and all other uses are obsolete. We now refer to the "enlargement of pregnancy" ("greatness" was a good word, but it isn't used much any more); the "swelling of inflammation;" Even the tumor of the passionate penis has been bowdlerized to "tumescent." Tumor is still occasionally used to refer to pregnancy, but only in unmarried ladies who go to out-of-town hospitals to have their "tumors" removed.
Most tumors either reach a finite size and stop growing, or grow very slowly. Warts or moles are, by definition, tumors, as are many other harmless (benign) swellings. If a tumor continues to grow so that it threatens the life of the individual, it is called malignant ("mal" means "bad"; "bene" means "good"). Malignant tumors are divided into several types according to the tissues of the body from which they come.
The tissues of the body can be divided into three broad categories: epithelium, connective tissue, and nervous tissue. Epithelium (epi= on, thelium=nipple; a word that now has a much broader meaning) is the tissue that covers the body surfaces, and everything that is derived from it or looks like it. The lining of your skin is epithelium, as is the lining of your mouth and intestine. Most of what makes up a piece of liver is epithelium, and a good part of what the kidney is composed of is also epithelium. The connective tissues include bone, muscle, and the cells and fibers that hold almost everything together (connective tissue proper). Steak consists largely of muscle, as does the heart. Leather is tanned connective tissue. The gristle in the meat you eat is also connective tissue. Nervous tissue is just called nervous tissue, which makes it one of the few medical terms that anyone can understand. Those malignant tumors derived from epithelium are called cancers or carcinomas. Those coming from connective tissue, bone, muscle, and other supportive tissues are called sarcomas (flesh tumors). Popular usage has made the word cancer synonymous with "malignant tumor" and I will use it in that way. Purists may be disconcerted when I talk about cancer of the blood cells or cancer of the bone, but that's the nature of language; what once was "on the nipple"now also refers to the cells of the kidney, the liver, the skin, the adrenal gland, and so on. Tumors of nervous tissue are simply called "nerve tumors" (neuromas).
This division of tumors into good (benign) and bad (malignant) is okay as far as It goes, but it doesn't go very far. There are bad tumors that are very bad, some that are not so bad, and many that might be bad it not removed. There are also some "good" tumors that are very bad if they are in the wrong place and "good" tumors that can become bad. There is even the rare "bad" tumor that turns over a new leaf.
Sometimes cells from a tumor that arise in one part of the body end up in another part and proceed to grow. A tumor of the breast can end up growing in the bone; a tumor of the lung can end up in the brain; or a tumor of the skin can end up in the lung. When this happens it is called metastasis. Some tumors metastasize readily, and some do not. It is obvious that cutting off a skin tumor may not help much if it's already growing in the lung as well as in the skin. The really bad tumors, therefore, do a lot of metastasizing. Why some tumors do this and others don't is poorly understood, and will be discussed in more detail later on.
This book is about tumors and cancers and malignant and benign and metastasis and a whole mess of words that terrify human beings. It is strange that the words "cancer" and "malignant" terrify people far beyond the actual dangers posed by the diseases that they represent. Cancer is no more terrible than many other ways of dying such as automobile accidents, heart disease, strokes, and a wide variety of terrible things which happen to people. It is as if the word "cancer" has become the scapegoat of all of our fears, so that people may feel that if they do not have cancer, they are healthy; and if they do have cancer that they are doomed. Nothing can be further from the truth. There are worse ways of dying than of cancer; and very many people who have cancer are cured and go on to lead full productive lives --only to eventually die of something else. The word "cancer" has been known to kill. People who thought they were doomed have taken their own lives rather than submit to what they believed to be a large amount of suffering. Words can kill; and it is one of the purposes of this book to deliver people from the terror of the words, so that the disease itself can be approached in a rational and meaningful way. I will try to explain what these words mean and what we do and don't understand about this biological process called cancer.