Benign and Malignant Tumors Tumors are not always malignant. Benign tumors can appear in any part of the body. Many of us have them—freckles, moles, fatty lumps in the skin—but they don't cause any problems except (sometimes) cosmetic ones. They can be removed or left alone. However they are treated, they stay in one place. They do not invade or destroy surrounding tissues.
Malignant tumors, on the other hand, have two significant characteristics:
• They have no "wall" or clear-cut border. They put down roots and directly invade surrounding tissues.
• They have the ability to spread to other parts of the body. Bits of malignant cells fall off the tumor, then
travel like seeds to other tissues where they land and start similar growths. Fortunately, not all the many
thousands of cancer cells that break off a tumor find a place to take root. Most die like seeds that go
unplanted.
This spreading of cancer is called metastasis . And doctors are always concerned about whether the cancer has metastasized during the silent period. If it has, then the migrating cancer cells have begun to go through their own silent period. They too are too small to detect for many months or years.
Almost all cancers share these two properties, although cancers arising in various organs tend to behave differently. They spread to different parts of the body. They grow in very specific ways that are characteristic of that cancer. The consequence is that there is a specific method of diagnosis, staging and treatment for each kind of cancer. One set of principles governs diagnosis and treatment of breast cancer, for example, while the rules for lung or colon cancers are just as complex but somewhat different.
