Keratinocyte Skin Cells

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Keratinocytes are the most common type of skin cells. They make keratin, a protein that provides strength to skin, hair, and nails. Keratinocytes form in the deep, basal cell layer of the skin and gradually migrate upward, becoming squamous cells before reaching the surface of the skin over the course of a month. For this reason, non-melanoma skin cancers such as basal cell carcinoma and squamous cell carcinoma are sometimes called keratinocyte cancers.

The most common type of keratinocyte cancer is basal cell carcinoma.

What Is Basal Cell Carcinoma?

Basal cell carcinoma is a type of skin cancer. Basal cell carcinoma begins in the basal cells—a type of cell within the skin that produces new skin cells as old ones die off.

Most basal cell carcinomas are thought to be caused by long-term exposure to ultraviolet (UV) radiation from sunlight. Avoiding the sun and using sunscreen may help protect against basal cell carcinoma.

Symptoms of Basal Cell Carcinoma

Basal cell carcinomas usually develop on sun-exposed parts of your body, especially your head and neck. A much smaller number occur on the trunk and legs. Yet basal cell carcinomas can also occur on parts of your body that are rarely exposed to sunlight.

Although a general warning sign of skin cancer is a sore that won't heal or that repeatedly bleeds and scabs over, basal cell cancer may also appear as:

  • A pearly white or waxy bump, often with visible blood vessels, on your face, ears or neck. The bump may bleed and develop a crust. In darker skinned people, this type of cancer may be brown or black.
  • A flat, scaly, brown or flesh-colored patch on your back or chest. Over time, these patches can grow quite large.
  • More rarely, a white, waxy scar. This type of basal cell carcinoma is easy to overlook, but it may be a sign of a particularly invasive and disfiguring cancer called morpheaform basal cell carcinoma.

Causes of Basal Cell Carcinoma

Basal cell carcinoma occurs when one of the skin's basal cells develops a mutation in its DNA. Basal cells are found at the bottom of the epidermis—the outermost layer of skin. Basal cells produce new skin cells. As new skin cells are produced, they push older cells toward the skin's surface, where the old cells die and are sloughed off.

The process of creating new skin cells is controlled by a basal cell's DNA. A mutation in the DNA causes a basal cell to multiply rapidly and continue growing when it would normally die. Eventually, the accumulating abnormal cells may form a cancerous tumor.

Ultraviolet Light and Other Causes

Much of the damage to DNA in basal cells is thought to result from ultraviolet (UV) radiation found in sunlight and in commercial tanning lamps and tanning beds. But sun exposure doesn't explain skin cancers that develop on skin not ordinarily exposed to sunlight. This indicates that other factors may contribute to your risk of skin cancer, such as being exposed to toxic substances or having a condition that weakens your immune system.

When to See a Doctor

Make an appointment with your doctor if you have any signs or symptoms that worry you.

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