The skin is the largest organ in our body. It provides protection against heat, cold, light, and infection. The skin is made up of two major layers (epidermis and dermis) as well as various types of cells. The top (or outer) layer of the skin is the epidermis, which is composed of three types of cells: squamous cells; basal cells; and melanocytes, cells that provide skin its color and protect against skin damage. The inner layer of the skin is the dermis, and is the layer that contains the nerves, blood vessels, and sweat glands.

Skin cancer is a disease in which cancerous (malignant) cells are found in the outer layers of your skin. There are several types of cancer that originate in the skin. The most common types are basal cell carcinoma (70 percent of all skin cancers) and squamous cell carcinoma (20 percent). Melanoma (5 percent of all skin cancers) is the third type of skin cancer. It is less common than basal cell or squamous cell cancers, but potentially much more serious. Other types of skin cancer are rare.

Every day, there are cells in our body such as basal cells and squamous cells that are exposed to the sun and damaged in ways that can make some of these cells grow rapidly out of control. Our immune system recognizes these cells as having lost control, and removes them. Occasionally, one of these cells slips past our defenses and becomes skin cancer. This starts as one cell and grows slowly. It happens with greater frequency as we get older because there has been more exposure to the sun and more opportunities for our immune system to miss one in error.


Basal cell carcinoma is the most common type of skin cancer. It typically appears as a small raised bump that has a pearly appearance. It will often have small little spider vessels called telangectasias. It is most commonly seen on areas of the skin that have receiving the most sun exposure. These cancers may spread to the skin surrounding them, but rarely spread to other parts of the body. A large proportion of theses occur on the head and neck due to excessive sun exposure, upper lip, nose, ears, forehead and neck.


Squamous cell carcinoma is also seen on the areas of the body that have been exposed to excessive sun (nose, lower lip, hands, and forehead). Often this cancer appears as a firm red bump or ulceration of the skin that does not heal. Squamous cell carcinomas can spread to lymph nodes in the area, but only rarely in the larger or more invasive types.


Melanoma is a skin cancer (malignancy) that arises from the melanocytes in the skin. Melanocytes are the cells that give color to our skin. These cancers typically arise as pigmented (colored) lesions in the skin with an irregular shape, irregular border, and multiple colors. ABCD reminds us to look for asymmetry, border irregularity, color variation and large diameter. It is the most harmful of all the skin cancers, because it can spread to lymph nodes or other sites in the body. Fortunately, most melanomas have a very high cure rate when identified and treated early.

How does the sun cause skin cancer?

Most skin cancers occur on sun-exposed areas of skin, and there is a lot of scientific evidence to support UV radiation as a causative factor in most types of skin cancer. Family history is also important, particularly in melanoma. The lighter your skin type, the more susceptible you are to UV damage and to skin cancer. A combination of blond hair, blue eyes, several severe childhood sunburns and a strong family history can triple your risk for melanoma.

How do you diagnose skin cancer?

The vast majority of skin cancers can be cured if diagnosed and treated early. Aside from protecting your skin from sun damage, it is important to recognize the early signs of skin cancer.

Look for:

  1. Skin lesions that regularly crack and bleed, or ulcers in the skin that won't heal.
  2. Change in color, size, border or symmetry.
  3. Sudden growth of a previously stable mole.
  4. New appearance of pigmented skin lesion.
  5. Hard or subcutaneous nodules developing under the skin lesion.

If you notice any of the factors listed above, see your doctor right away. If you have a spot or lump on your skin, your doctor may remove the growth and examine the tissue under the microscope. This is called a biopsy. A biopsy can usually be done in the doctors office and usually involves numbing the skin with a local anesthetic. It is then sent to a pathologist to look at under a microscope. It cannot be diagnosed by vision alone.

How do you treat skin cancer?

There are varieties of treatments available to treat skin cancer, including surgery, radiation therapy, and chemotherapy. Surgery is the most common form of treatment. It generally consists of an office or outpatient procedure to remove the lesion and check edges to make sure all the cancer was removed. For basal cell and squamous cell carcinomas, excision is frequently done using a specific technique called Mohs micrographic surgery, which gives the best chance to include all margins, while still minimizing the size of the defect.

Depending on the size of the defect, your doctor may take some skin from somewhere else to cover the wound and promote healing. This part is called reconstruction and is the most complicated part of the surgical aspect of treatment. Closures range from simple stitches to tissue rearrangement and skin grafting. Tissue rearrangement is like fitting together pieces of a puzzle in a way that will make it look most like the original appearance. This could include borrowing skin from your cheek to fill the skin lost at the side of the nose. It almost always requires a scar, but often is a better match than taking skin from somewhere else to fill the defect.

Melanoma treatment is more extensive and your doctor might also recommend doing a biopsy of the lymph node with the best chance of having tiny microscopic metastatic cancer cells. This is called a sentinel lymph node biopsy, and further removal of more lymph nodes might be needed if this biopsy is positive. Sometimes radiation may be used as definitive therapy or after surgery, depending on the situation. For melanomas, biochemotherapy that will train and help the immune system may be used in more advanced cases.

Who is at risk for skin cancer?

People with any of the factors listed below have a higher risk of developing skin cancer and should be particularly careful about sun exposure.

How can I prevent skin cancer?

The single most important thing you can do to lower your risk of skin cancer is to avoid direct sun exposure. Sunlight produces ultraviolet (UV) radiation that can directly damage the cells (DNA) of our skin. People who work outdoors are at the highest risk of developing skin cancer. The sun's rays are the most powerful between 10 am and 2 pm, so be particularly careful during those hours. In Arizona, those hours may be longer and the amount of time in the sun can be very short before being overexposed. If you must be out during the day, wear clothing that covers as much of your skin as possible, including a wide-brimmed hat to block the sun from your face, scalp, neck, and ears.

The use of sunscreen can provide protection against UV radiation. When selecting a sunscreen, choose one with a Sun Protection Factor (SPF) of 15 or more. For people who live in Arizona, a SPF of 30 or greater should be used during summer and when prolonged exposure is anticipated. Sunscreen should be applied before exposure and when the skin is dry. If you will be sweating or swimming, most sunscreens need to be reapplied. Sunscreen products do not completely block the damaging rays, but they allow you to be in the sun longer without getting sunburn.

It is also critical to recognize early signs of skin trouble. The best time to do self-examination is after a shower in front of a full-length mirror. Note any moles, birthmarks, and blemishes. Be on the alert for sores that do not heal or new nodules on the skin. Any mole that changes in size, color, or texture should be carefully examined. If you notice anything new or unusual, see your physician right away. If you have a strong family history of skin cancer, particularly melanoma, an annual examination by a physician skilled at diagnosing skin cancer is recommended. Catching skin cancer early can save your life.

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