Facts on File Encyclopedia of Health and Medicine

skin cancer Malignant growth that arises from
the epidermis or dermis. There are many types of
CANCER that occur in the SKIN. The three most
common types of skin cancer are basal cell carci-
noma, squamous cell carcinoma, and malignant
melanoma. Skin cancer is the most widely diag-
nosed type of cancer in the United States, with
about 1 million new cases each year. The vast
majority of skin cancers—basal cell carcinoma and
squamous cell carcinoma—are nearly 100 percent
curable with early detection and treatment. Malig-
nant melanoma, the least common form of skin
cancer, is more dangerous because it tends to
metastasize (spread) early in its development,
though it also has a high cure rate when detected
and treated before it metastasizes.
Cancer experts believe nearly all skin cancer
results from sun damage to the cells of the skin.
The ultraviolet lightwaves the sun emits cause
subtle changes in the ways skin cells function.
Over time these changes can result in aberrant
growth, causing skin cells to form into cancerous
lesions. People with fair skin are most vulnerable
to this damage, as their skin produces less
melanin. In addition to giving the skin its color,
melanin protects the skin from the sun by absorb-
ing the ultraviolet lightwaves that cause damage.
A tan paradoxically results from and protects the

skin against sun exposure, as sun exposure stimu-

lates melanocytes to produce melanin.

The ultraviolet light used in tanning

booths affects the SKINin the same way

as the ultraviolet lightwaves of the sun,

and carries the same exposure risk for

skin cancer.

The correlation between sun exposure and skin

cancer also means that nearly all skin cancers are

highly preventable. Cancer experts recommend

diligent SUN PROTECTION measures beginning in

early childhood in combination with regular skin

examinations to detect suspicious growths or

changes in existing lesions. Other types of cancer

that can affect the skin, but are not primary skin

cancers or related to sun exposure, include

KAPOSI’S SARCOMA, primarily a manifestation of

HIV/AIDSin the United States, and cutaneous T-cell

LYMPHOMA.

Basal Cell Carcinoma

Basal cell carcinoma is a cancer of the ker-

atinocytes that form the bottom, or base, of the

epidermis, also called basal cells. Most basal cell

carcinomas erupt around HAIR follicles, leading

researchers to suspect they originate in the follicle

196 The Integumentary System

HEALTH CONDITIONS THAT MAY AFFECT THE SKIN

ACNE ACROCHORDON ACTINIC KERATOSIS
ALBINISM BIRTHMARK BLISTER
BULLA BULLOUS PEMPHIGOID CALLUS
CARBUNCLE CELLULITIS CORNS
CRADLE CAP DECUBITUS ULCER DERMATITIS
DISCOID LUPUS ERYTHEMATOSUS(DLE) EPIDERMOLYSIS BULLOSA ERYSIPELAS
ERYTHEMA MULTIFORME ERYTHEMA NODOSUM FOLLICULITIS
FROSTBITE FURUNCLE HYPERHIDROSIS
ICHTHYOSIS IMPETIGO KAPOSI’S SARCOMA
KELOID LICHEN PLANUS LICHEN SIMPLEX CHRONICUS
MILIARIA NEVUS PAPILLOMA
PEDICULOSIS PEMPHIGUS PILONIDAL DISEASE
PITYRIASIS PRURIGO PSORIASIS
ROSACEA SCABIES SEBORRHEIC KERATOSIS
SKIN CANCER SUNBURN TINEA
TOXIC EPIDERMAL NECROLYSIS URTICARIA VITILIGO
WART WHITLOW XANTHOMA