Risks of Getting Melanoma Cancer

What is Melanoma?

Malignant Melanoma is a cancer of the melanocytes, which are the pigment-forming cells in the skin.

The melanocytes are special cells that produce a pigment, called melanin, which gives us our coloring. Black people have more melanin production in their skin, while Caucasians have less. Albinos have none at all. Their skin is pure white and their eyes are light blue or pink. Besides for the skin, melanin-producing cells are also found in the mouth, eye, gut and vaginal areas.

A cancer starting in the melanocytes is called a "melanoma." If someone develops melanoma, it is critical to get prompt diagnosis and proper treatment; this can literally make the difference between life and death. Fortunately, newer treatments give greater hope for melanoma patients than before.

Interestingly, in early womb life, the melanocytes develop from the same cells which ultimately form the brain and nervous systi. The skin is the most common site for melanoma to develop, since it contains the most melanocytes. Besides being found in the skin, melanocytes are also found in the eye, in the anal/rectal region, in the linings of the mouth and in the vagina. Some are even found in the gut and central nervous systi (brain and spinal cord). Any of these areas can develop melanoma, but much less commonly than the skin. It is quite common, however, for a melanoma starting in the skin to spread ("metastasize") to other areas with melanocytes.

The area where a cancer first starts is called the "primary site", as distinguished from later areas of spread. The "primary site" is usually apparent for most cancers, but not uncommonly it remains "hidden" in melanoma-- the first sign of disease being distant metastasis. Thus, it is common to first detect metastatic melanoma in the lung, bone or brain, although its primary site was probably the skin.

The skin is a tissue, meaning that it is a collection of cells organized as a unit. Cells are the smallest level of animal life, and are controlled by the genetic material called "genes" within them. Initially all human cells start out from the fusion of the sperm and egg cell; at the time of fertilization there is only one type of cell ("zygote") containing genetic information for constructing the entire human body. As the body is formed, cells differentiate into all sorts of specific subtypes, such as nerve, muscle, liver and heart cells. As they do so, part of the genetic material in them is "masked" so that it becomes unavailable; we do not need information on how to form a bone cell when we are making a stomach cell! However, every cell still retains, at some level in its genes, the total information necessary for constructing an entirely new body. This is how scientists are able to clone a cheek cell, for instance, into a whole new animal.

Normally, skin cells divide very quickly in womb life, early childhood and through puberty to form the covering surface or "integument" of our bodies. In adulthood, they divide more slowly to replace cells that have died either from old age or injury. New skin cells arise at the deepest level of the skin, and gradually push their way upwards toward the surface as they mature. The main types of cells found within the skin are basal cells, which form the bottom layer, squamous cells, which push toward the surface to form the skin we see, and melanocytes, which produce melanin pigment that colors the skin.

If specific types of gene damage occurs in a cell, it can start dividing out of control. When cells divide quickly, they tend to pile up to form a lump, called a "tumor". A tumor merely means an abnormal swelling; it can be caused by infection, inflammation, or just about anything and is usually not cancer. A "benign" tumor only grows in its local area (albeit quite large), it cannot spread distantly and is not cancer. In contrast, a "malignant" tumor has the ability to spread to anywhere in the body, and this is cancer. The process of spreading is called "metastasis", and is what makes cancer so dangerous. Ultimately, cancer starts in a single cell and and is a disease of its genes. Any type of skin cell can give rise to skin cancer, when their reproduction goes out of control, and they divide in a disorganized way. When basal or squamous cells become cancerous, they are called carcinomas, while when the melanocytes become cancerous, this is called melanoma, which has such a different character that it is a different topic than other skin cancers.

How Common is Melanoma?

In 1997 in the United States 38,000 new cases of melanoma were diagnosed, and 7,300 deaths were attributed to the disease. The number of new cases of melanoma has tended to rise each year. In 1935, the lifetime risk of getting melanoma was only 1 in 1500, but had increased to 1 in 135 by 1990. It is effecting 1 in 90 people by 2000. While it is rare in young children, it begins to occur in puberty, and then increases each year through age 70, afterwhich it decreases. The more fair skinned a person is, the higher their risk to develop melanoma, of any body area. Conversely, it is very rare in dark black individuals. It is more common in predominantly fair-skinned countries, such as Australia.

What Causes or Increases the Risk for Melanoma?

Like any cancer, no one knows exactly why one individual gets melanoma and another does not. The exact cause of any cancer is currently unknown. However, several risk-factors have been discovered by studying groups of people affected:

1) Sun Exposure increases the risk of all skin cancers, including melanoma. One of the reasons that melanoma has increased over the years is thought to be people spending more time "sun bathing" at the beach. More melanoma is noted in people living in sunny climates (i.e. Florida) than weak-sun areas (i.e. Alaska). Ocular (eye) melanoma is also more common in sunny areas, but not melanomas occurring deeper within the body.

2) Heredity - People with a family history of certain conditions make up about 10% of melanoma patients. These "melanoma families" have genes of "dominant" heredity, which means that if one parent has it, it will most likely be passed to their children. However, it is "incompletely penetrant", which means it won't necessarily be expressed in the offspring, even if they have it. Family members of those with these hereditary genes will tend to get melanoma at a younger age than the other 90% of individuals who develop melanoma sporadically. They are also more likely to have multiple sites of melanoma, which occurs in 5% of all people affected.

Particular syndromes associated with high risk for melanoma are "Dysplastic Nevus Syndrome" and "Atypical Mole Syndrome". A "nevus" is a pigmented area of skin, which may be raised, often called a "mole". Patients may have hereditary conditions where they have large or unusually shaped moles, which are filled with melanocytes. The odder shaped ("dysplastic") or more abnormal ("atypical") they appear, the more likely to become cancerous. Also, the more the moles are irritated by sunlight or chemicals, the greater the chance that they will undergo "malignant degeneration" to become cancerous.

3) Nevi ("moles") in themselves will increase the risk for skin melanoma. About 70% of skin melanoma have a pre-existing mole at the cancer site; this is one reason why one of the famous "7 signs of cancer" includes a change in a wart or mole. Interestingly, people continue to develop nevi throughout life. By age age 30, men have about 40 nevi that were not present at birth, mostly on the trunk and arms. This is one reason why the incidence of melanoma increases with age. Fortunately, only one of a million moles moles becomes malignant.

4) Chronic Irritation is a the underlying the development of many types of cancer. Irritants include chemicals ("carcinogens"), ultraviolet light, radiation, and trauma causing scars to form in an area. Anything that damages cells over time will cause specific cells in damaged areas to divide and try to repair damage. The more divisions, the more chance of something going awry in the division mechanism leading to uncontrolled growth -- this is cancer and starts with a "screw-up" in just a single cell. Thus anything which is continuously irritating (i.e. cigarette smoke, b sunlight) should be avoided to minimize the risk of developing any type of cancer over time.

5) Poor Immune System Function or Immunosuppression raises the risk for many cancers, including melanoma. There is a theory called "immunosurveill- ance" which says that we are developing cancerous cells all the time, but that a healthy immune system recognizes and destroys them before they can start to divide, take root and spread. Many factors are associated with decreased immune system function, including viruses like HIV, EBV, CMV and Hepatitis, certain medications ("immunosuppressants"), poor nutrition, diabetes, and even feeling emotionally depressed over time. These conditions can "promote" the development of cancer, especially in genetically predisposed individuals.