Definition of Skin Cancer

Skin CancerSkin 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 carcinoma, squamous cell carcinoma, and malignant melanoma.

Skin cancer is the most widely diagnosed 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.

Malignant 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.

Skin Cancer and Sun Damage

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 absorbing the ultraviolet lightwaves that cause damage. A tan paradoxically results from and protects the skin against sun exposure, as sun exposure stimulates melanocytes to produce melanin.

The ultraviolet light used in tanning booths affects the skin in 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/AIDS in the United States, and cutaneous T-cell Lymphoma.

Basal Cell Carcinoma

Basal cell carcinoma is a cancer of the keratinocytes 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 structure or the sebaceous gland (sometimes collectively called the pilosebaceous unit).

Basal cell carcinomas nearly always arise on sun-exposed skin surfaces, though may also occur on skin exposed to radiation such as for radiation therapy.

The characteristic symptoms of basal cell carcinoma are:

  • Open sore that does not heal
  • Reddened or flaky patch that itches or hurts
  • Shiny, discolored nodule (bump) that develops on the skin
  • Pinkish, craterlike structure with raised edges and tiny blood vessels visible in the center
  • Yellowish, waxy area that resembles a scar though gradually enlarges and may itch

Though basal cell carcinomas rarely metastasize, they do spread within the epidermis and can cause considerable damage to the skin. Doctors diagnose about 800,000 Americans with basal cell carcinoma each year, making it the most common cancer of any type.

A person who has one basal cell carcinoma is likely to develop others, though removed tumors seldom recur.

Basal cell carcinoma is uncommon in dark-skinned people

Squamous Cell Carcinoma

Squamous cell carcinoma is a cancer of the keratinocytes in the upper layer of the epidermis, formerly called squamous cells because of their squamous, or squashed, appearance. Nearly all squamous cell carcinoma evolves from actinic keratosis (though not all actinic keratosis lesions become cancer).

Because of this, doctors consider actinic lesions precancerous and remove them to end their progression, effectively thwarting the cancer’s development. Squamous cell carcinoma can but does not often metastasize. Sun damage causes most squamous cell carcinoma, though tumors can form in sites of continual irritation.

The characteristic symptoms of squamous cell carcinoma are:

  • Crusted, raised growth resembling a wart that easily or frequently bleeds
  • Patch of red, flaky skin that oozes or bleeds
  • Sore that bleeds and crusts but does not go away
  • Ulceration on the lips that resembles a cold sore but does not heal

Though most commonly a cancer of the surface skin (particularly sun-exposed), squamous cell carcinoma also can develop in the mucous membranes. Untreated squamous cell carcinoma will eventually grow downward to penetrate the dermis and subcutaneous layer, and may spread to lymph structures that enable widespread metastasis.

Doctors diagnose about 200,000 Americans with squamous cell carcinoma each year

hough squamous cell carcinoma is less common in darkskinned than in light-skinned people, among skin cancers in dark-skinned people squamous cell carcinoma is the most common.

Malignant Melanoma

Malignant melanoma arises from melanocytes, the cells that produce melanin. Benign skin lesions such as nevi (moles) composed of melanocytes are often the staging sites for malignant melanoma. Malignant melanoma can develop and metastasize quickly. Diligent monitoring for changes in existing lesions such as moles is the most effective method for early detection and diagnosis.

Doctors classify malignant melanoma by growth pattern (such as nodular, superficial, or spreading) or by depth of invasion, metastasis, and nodal involvement.

Small, localized malignant melanomas are about 90 percent curable with early diagnosis and treatment. Widely metastasized malignant melanoma is usually fatal.

The characteristic symptoms of malignant melanoma are

  • Change in the size, symmetry, color, or texture of an existing nevus (mole)
  • Bleeding or oozing from an existing nevus
  • A new nevus that emerges and grows rapidly, especially one that has asymmetrical shape, irregular borders, multiple colors, or exceeds one quarter inch in diameter (the ABCD criteria)

Doctors diagnose about 50,000 Americans with malignant melanoma each year, many of whom have moderate to advanced cancer by the time of diagnosis.

A = asymmetry;halves do not match
B = borders;edges are irregular or vague
C = color;two or more colors are present
D = diameter;larger than one quarter inch

Symptoms and Diagnostic Path

Symptoms vary among the types of skin cancer, though generally any wound or sore that does not heal or mole that changes appearance is suspect. The diagnostic path typically includes biopsy of suspicious lesions. The dermatologist may remove very small lesions without biopsy, as doing so effectively removes any cancer that is present.

Biopsy identifies the type of cancer present, which determines the appropriate course of treatment.

Characteristic Skin Cancer Symptoms
Type of Skin CancerCharacteristic Symptoms
basal cell carcinomasore that does not heal
persistent red or flaky patch that itches
shiny, discolored nodule
vascular crater
yellowish, waxy, itchy plaque
squamous cell carcinomawartlike lesion that bleeds
flaky patch that bleeds
sore that repeatedly bleeds and crusts
lip ulceration that does not heal
malignant melanomaABCD criteria:

  • asymmetrical appearance
  • irregular borders
  • multiple colors
  • diameter greater than one quarter inch

Treatment Options and Outlook

The preferred treatment for nearly all skin cancer is surgical removal, which may include various methods such as curettage and electrodesiccation (scraping and cauterization), excision (cutting out), and Mohs’ micrographic surgery. Microscopic examination of the removed lesion confirms the diagnosis and type of cancer. Malignant melanoma requires extensive excision, with wide margins and possible removal of nearby lymph nodes, and may require follow-up chemotherapy if the cancer has metastasized.

Dermatologists may use cryotherapy (liquid nitrogen) to remove precancerous lesions, such as those of actinic keratosis, and very small lesions that appear suspicious. Other treatment options may include topical imiquimod (Aldara) cream and radiation therapy.

Risk Factors and Preventive Measures

The single-most important risk factor for skin cancer is excessive sun exposure. People born before the 1980s have the highest risk for skin cancers because they grew up before sunscreen products became available.

Skin cancers tend to manifest several decades after the exposures that damaged the skin, making it important for people age 40 and older to have yearly skin examinations from a physician and to perform monthly skin self-examination.

People who have had skin cancers removed may need more frequent physician evaluation. The most effective preventive measures are those that safeguard the skin from sun damage. These measures include

  • Limit sun exposure during peak ultraviolet intensity (10 a.m. to 2 p.m. in most of the United States)
  • Wear protective clothing to cover the skin
  • Apply sunscreen liberally and frequently before and during sun exposure


How did you like this article?

Page last reviewed:

About Us