Skin Cancer

I

Introduction

Skin Cancer, malignancy in the skin, and the most common of all cancers. Every year more than a million Americans are diagnosed with skin cancer. The most common skin cancers are easily cured and are rarely life-threatening unless left untreated. Ultraviolet radiation (UV) from sunlight is the major cause of skin cancer. To prevent skin cancer, physicians recommend that people avoid exposing their skin to sunlight, especially when the sun is strongest—between 11 am and 3 pm.

II

Types of Skin Cancer

Skin cancers develop in the epidermis, the outer layer of skin. There are three main types of skin cancer, classified by the kind of skin cell affected: basal cell carcinoma, squamous cell carcinoma, and melanoma. The vast majority of skin cancers are basal cell or squamous cell.

Basal cell carcinoma, the most common type of skin cancer, develops in the basal, or bottom, layer of the epidermis. It usually occurs in areas exposed to sunlight, especially the head and neck. It grows slowly and rarely spreads, but it can recur.

Squamous cell carcinoma, the second most common type of skin cancer, develops in the upper layers of the epidermis. It can appear as lumps, often reddish in color. It frequently occurs in areas exposed to sunlight, including the face, neck, and back of the hands, but sometimes occurs elsewhere on the body. It is somewhat more likely to spread to the lymph nodes than basal cell cancer is.

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The third type of skin cancer, melanoma, develops in melanocytes, or pigment cells, that are found throughout the basal layer. Melanoma is the most dangerous type of skin cancer and accounts for the vast majority of skin cancer deaths. It is about ten times more common in whites than in African Americans.

A rare and aggressive form of skin cancer, called Merkel cell carcinoma, forms in hormone-making skin cells known as Merkel cells. It primarily strikes older people and people who have weakened immune systems as a result of human immunodeficiency virus (HIV) infection. Researchers have linked Merkel cell carcinoma to a virus.

III

Risk Factors

Skin cancers can grow in any part of the skin, but approximately 90 percent develop in areas exposed to the sun, especially the face, neck, backs of the hands, and the scalps of bald men. Exposure to direct sunlight, especially during childhood, is the chief risk factor for skin cancer. The greater the number of severe sunburns a person has had, the greater the risk of developing skin cancer later in life. People with pale skin are at greatest risk for skin cancer, particularly if their skin burns or freckles easily. Men are at greater risk of skin cancer than women.

Someone who has had skin cancer is at high risk of developing it again. A family history of skin cancer increases the risk of melanoma. Radiation therapy also increases the chances of developing skin cancer in the area exposed to the radiation. Skin damaged by severe burns or by certain skin diseases is also at increased risk of cancer.

IV

Symptoms and Diagnosis

Early detection and treatment are the keys to survival, especially for melanoma. Any of several skin changes may signal skin cancer and should be reported to a physician. These include any change in the size, shape, color, or texture of a mole or other darkly pigmented area; any mole that begins to itch or becomes tender; the development of a new mole or other growth, particularly if it feels hard; any mole or other growth that spontaneously or persistently bleeds; a sore that does not heal; and a black spot under a toenail or fingernail that extends beneath the cuticle.

Basal cell carcinomas may be flat, firm, and pale, or appear as raised, pink or red, shiny areas. They may bleed from a minor injury. Squamous cell carcinomas may appear as lumps with a rough or scaly surface, or as flat, reddish patches.

Melanomas often begin as tiny molelike growths that then grow bigger and change their color. Melanomas are generally tan, brown, or black. The American Cancer Society recommends an ABCD rule for spotting melanoma. A stands for asymmetry—the halves of the growth do not match in shape. B stands for border irregularity—the growth has a ragged border. C stands for color—the color of the growth is uneven. D stands for diameter greater than 6 millimeters (about the size of a pencil eraser).

To confirm a diagnosis of skin cancer a physician usually performs a biopsy, removing a small piece of the skin to examine under a microscope for the presence of cancerous cells.

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