What is Cancer?

What is cancer? This seemingly simple question comes up a lot, especially when one is faced with a new diagnosis of this seemingly mysterious and frightening disease. Here is the answer...

Cancer is a general term for a variety of diseases which can affect the body. While there are many different types of cancer, they all have a few things in common.

First, to understand cancer, we need to define two terms. A tumor, derived from the Latin for "swelling", is any mass that occurs in a persons body. It is an abnormal growth of tissue which occurs because certain cells in the tissue malfunction and begin growing and dividing. The characteristics of various tumors can vary greatly, depending on the cell and tissue types from which they originate and their behavior in the body.

Secondly, the term malignant (mal means "bad" in Latin) refers to a tumor which is more aggressive. Some tumors tend to grow slowly and are less invasive in the body, not invading neighboring or distant tissues or organs readily. These are generally termed benign. Malignant tumors on the other hand typically grow faster, are more invasive (meaning they grow into and are more destructive of normal tissues around it) and tend to spread in the body. Spread of malignant tumors to distant sites in the body, either by the bloodstream or by the lymphatic system, is termed metastasis.

Now that we understand the terms tumor and malignant, we can fully answer "What is Cancer?" Cancer is a malignant tumor. It is as simple as that. It is a growing mass of abnormal cells which are invasive in the body and tend to spread in the body.

The specific causes of cancer are varied but most cancers are the result of mutations of the genetic material in cells (the DNA) which help control each cell's function. Mutations occur because of damage to the DNA which can occur sporadically, by exposure to carcinogens (compounds that tend to damage DNA) and by exposure to other things that damage DNA, such as radiation. Only when multiple specific mutations affect the same cell will that cell become malignant. The risk factors that lead to specific cancers vary considerably and will be discussed along with each specific cancer type.

While the answer to "What is Cancer?" above is a general one, applying to all types of cancer, each type of cancer can vary quite considerably. Most cancers are named for their cell, tissue or organ of origin. A simple example is something like lung cancer, which is a malignant tumor that originates from cells in the lungs. Cancers also vary in how aggressive and invasive they are. While all cancers are malignant, their degree of malignancy varies. Malignant versus benign is not black and white, it is a spectrum of behavior of the tumor cells with quite a bit of variability. The behavior and characteristics of each form of cancer are different. There are even some cancers which are not solid masses, but are rather a "liquid tumor" that spreads out in the bloodstream, such as leukemia.

Now that you understand the answer to "What is Cancer?", you may wonder why cancer, a malignant tumor, is potentially dangerous and even fatal. In a very general sense, the invasive nature of cancers leads to damage and destruction of other normal, previously-healthy tissues in the body. The growing tumor compromises these tissues which can lead to symptoms of cancer. Ultimately, if enough tissues or organs are compromised, either through local invasion or by distant spread by metastasis, the disease can kill the patient.