Skin Cancer Overview (cont.)

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What causes skin cancer?

The exact cause of skin cancer is not known. It appears that basal cell cancers arise from basaloid cells in the upper layer of the skin. Uncontrolled growth of these cells is regulated by other factors in the skin. When that regulation is lost, skin cancer cells begin to grow into tumors.

In squamous cell cancers, the tumors arise from a normal cell in the top layer of the skin, the epidermis. As with basal cell cancers, these cells are prevented from growing wildly by genetically controlled factors. When there is an alteration in the genes that regulate these cells, the control is lost and skin cancers start to grow. In many instances, the genes are altered by sunlight exposure.

What are the different types of skin cancer?

There are several different types of skin cancers:

  • Basal cell carcinoma is the most common cancer in humans. Over 1 million new cases are diagnosed in the U.S. each year. There are several different types of basal cell carcinoma, including the superficial type, the least worrisome variety; the nodular type, the most common; and the morpheaform, the most challenging to treat because the tumors often grow into the surrounding tissue (infiltrate) without a well-defined border.
  • Squamous cell carcinoma accounts for about 20% of all skin cancers but is more common in immunosuppressed people. In most instances, its biologic behavior is much like basal cell carcinoma, with minimal chance of spread. However, some of these tumors can act in an aggressive fashion and can even metastasize and cause death.
  • Less common skin cancers include melanoma, Merkel cell carcinoma, atypical fibroxanthoma, cutaneous lymphoma, and dermatofibrosarcoma.

What are the signs and symptoms of skin cancer?

Most basal cell carcinomas have few if any symptoms. Squamous cell carcinomas may be painful. Both types of skin cancer may appear as a sore that will not heal. There is often a slowly growing bump on the skin that may bleed after minor trauma. Basal cell carcinomas may have a pearly color while squamous cell carcinomas may have a thick scale on the surface. Both may have raised edges and a central ulceration.

Medically Reviewed by a Doctor on 12/12/2014

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