Cancer is a strange type of disease. It is not contageous and you can't catch it. Some toxins like tobacco and radiation seem to trigger it, but not everyone gets it from them, nor does everyone exposed get the same disease in the same body cells. And once started, cancer keeps going, well supported by the processes of the body to supply it with nutrients and grow.
Other than the word "cancer", there are many different other names for different types of cancers: leukemias, sarcomas, carcinomas, lymphomas, melanomas, and so on. Let us attempt to clarify all these terms.
The first distinction is whether a tumor is solid or dispersed. A single solid tumor is the best known idea of cancer, but some cancers are dispersed throughout the body without creating a single tumor, or creating a myriad of small tumors. Below is a classification of the common cancers into solid tumors and dispersed:
- Solid tumors: most body part cancers (lung cancer, breast cancer, ovary cancer, prostrate cancer, bowel cancer, brain cancer, testicular cancer, etc.) and their subcategories (sarcomas, carcinomas, melanomas, etc.).
- Dispersed: leukemias, lymphomas (e.g. Hodgkin's disease, Non-Hodgkin's lymphoma).
All types of cancer involve an overgrowth of cells. In a solid tumor, the cancer cells stay in one place, grow in a clump creating a tumor, and then might ultimately spread to create other new tumor clumps in other parts of the body. The name given to a cancer is typically based on where the tumor occurs. Actually cancers are named based on what type of cells are overgrowing, and with solid tumors, these cells tend to stay where they originated (though they can later spread). Hence, pancreatic cancer is a tumor of pancreas cells, lung cancers contain lung cells, and so on.
For a non-solid tumor, there is an overgrowth of cells but they never get a chance to clump together because they are dispersed throughout the body and are in continual motion. These cancers are those that affect the cells of a circulating system. The body's two main systems are the blood system and the less well-known lymph system. Leukemias are dispersed cancers of white blood cells and lymphomas are dispersed cancers of the lymph system.
Benign or malignant: A solid tumor is generally classed as either benign or malignant. Benign is good, malignant is bad. Both benign and malignant tumors contain cells that are growing when they should not. A benign tumor is one that is usually growing slowly and will not spread to other body parts. Any tumor that has spread via metastisis is malignant. A benign tumor can still cause some localized damage by taking up space and pressing on other body organs or glands near it. A benign tumor can also cause problems if it is a tumor of a hormone or enzyme production cell, which can lead to over-production of an enzyme or hormone in the body, though it is unclear whether such tumors will be classed as benign or malignant. A malignant tumor can cause local damage or hormone over-production, like a benign tumor, but its worst damage is usually by late-stage spreading from its original tumor site to other sites throughout the body and thus damaging many body organs.
Spreading (metastisis): The spreading of a tumor is called metastisis. It is a late-stage process for a solid tumor and is extremely dangerous. A metastisized tumor can create numerous new tumors throughout the body. Usually only solid tumors can spread in this way.
How do cancers spread? A cancer will typically spread through one of the circulatory systems: the blood or the lymph. Less commonly it can also spread through the serosal surfaces of the central nervous system.
Many types of cancers have typical patterns of spread. For example, breast cancers typically spread initially via the lymph. The reasons for these characteristic sequences for many types of cancers is not fully known.
Single cell origin: It is believed that cancers arise from
a single mutated cancer cell.
Any human cell seems capable of starting a tumor,
on any surface cell,
in any organ,
in any glands,
in the red or white blood cells,
even fat and muscle cells.
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