Cancer is a pot that holds many kinds of stew. This family of similar diseases is so broad and so variable that it’s almost impossible to make statementhat are true in all cases. Here’s one: Every cancer is different.
It’s important to distinguish between terms that are often used interchangeably: A “cancer” is a disease caused by uncontrolled cell division. “Malignancy” is a characteristic of the disease we call cancer and is present in greater or lesser degrees depending on the type of cancer as well as within the cancer itself. A “tumor” is a lump, nothing more or less, regardless of the degree of malignancy present. Some cancers, like melanoma, tend to form solid tumors. Other cancers, like leukemia, are diffusely spread throughout the body. Any cancer may be more or less malignant in character. The degree of malignancy usually increases as the cancer develops.
Cancer is a genetic disease. DNA strands are delicate and easily damaged by ionizing radiation (UV in sunlight, x-rays), chemical mutagens (any of a plethora of hydrocarbons and alkaloids), and errors in DNA replication that take place during normal, necessary cell division. Small changes in a cell’s genetic code can inactivate genes that put the brakes on cell division or prevent cells from moving out of their normal location. The behavior of normal cells is strongly influenced by signals from the tissue around them. Cancerous cells very often ignore those signals: they are often the worst cellular neighbors imaginable.
One must think of cancer cells as a family. Each successive generation of cells show more and more genetic derangement. As the disease progresses, mutations and genetic aberrations accumulate. The great-great-granddaughter cells of relatively mild cancer often lose any resemblance to the cell type from which they arose. This process, called “anaplasia,” results in cells with only the most primitive of traits. They wander freely from their site of origin and settle at random, then reproduce freely.
If you could walk through the cell nucleus of an anaplastic cell, you’d see nothing like a normal cell nucleus: Chromosomes may be multiplied or missing, with pieces of genetic material grafted together haphazardly. Cell division takes place constantly, but instead of dividing in two, the cell might divide into four cells, or double it’s genetic material and not divide at all, leaving it “polyploid” with two or more nuclei. Many of these cells are so deranged that they simply die in place, flooding the body with toxic cellular debris.
What causes cancer? You won’t like the answer. Cancer happens because it CAN happen. Any piece of complex machinery will have certain possible modes of failure and the genetic reproductive machinery of our cells is no different. The very characteristics of our cells that allow us to heal a wound or repair worn out tissues make it possible for malignancies to arise. Yes, our bodies monitor and eliminate cells with genetic problems, but no system is perfect. Sooner or later something happens that our defenses can’t identify or control.
Then what? Many cancers begin as fairly benign growths. Sure, the cells reproduce with little regard for the rules of the tissue in which they arise, but the initial generations of cells are often relatively well behaved. If the cancer can be detected early enough, it can be eliminated by surgery. There is something wonderfully direct about taking knife in hand, cutting disease out of a patient’s body and making them free of cancer, but the approach requires both luck and skill.
One impediment to surgical success is the behavior of the granddaughter cells described above. When the visible mass of a tumor has been completely removed, all that may be left are the much more malignant later generation cells that have already migrated invisibly into surrounding or distant tissues. More than any other factor, this phenomenon requires us to be vigilant in searching for possible cancers, to investigate suspected malignancies immediately, and to act quickly and aggressively in removing cancers whenever we find them BEFORE the inevitable progression of malignancy make a surgical cure impossible. Other approaches, such as chemotherapy and radiation are required to treat disseminated malignancies or those in which surgery isn’t appropriate.
Where cancer diagnosis and treatment are concerned, waiting is usually the worst possible option. If your pet has a suspicious lump or bump, see your veterinarian immediately. Don’t put off seeking care. If you allow a cancer time to develop, your options disappear and you’ll be left with only the choices you would rather avoid – or no choice at all.