Damage in the epidermis to the normal DNA of skin cells may result in new cells growing out of control, and eventually forming an accumulation of cancer cells.
Much of the damage to DNA in skin cells results from ultraviolet (UV) radiation found in sunlight and in commercial tanning lamps and beds. UV light is divided into three wavelength bands, including ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC). Only UVA and UVB rays reach the earth. UVC radiation is completely absorbed by the atmospheric ozone. UVA and UVB rays play a role in the formation of skin cancer by causing changes in skin cell DNA, including the development of oncogenes, which are types of genes that can turn a normal cell into a malignant one. UVA penetrates the skin more deeply than UVB.
Tanning beds deliver high doses of UVA, which makes them especially dangerous. UVA puts an individual at greater risk of skin cancer than spending long hours in the sun because of the deep penetration of the rays.
Other factors: Heredity, exposure to toxic chemicals, and radiation treatments may also cause skin cancers.
Most doctors recommend a checkup for skin cancer when a new skin growth, a bothersome change in the skin, a change in the appearance or texture of a mole, or a sore that doesn't heal in two weeks appears.
Biopsy: If the doctor suspects skin cancer, a small sample of the skin (biopsy) will be removed and analyzed. A biopsy can usually be done in a doctor's office using local anesthetic.
Squamous cell carcinoma: A biopsy is often the only test needed to determine if the individual has squamous cell carcinoma. This cancer doesn't spread, and larger growths may require further testing.
Basal cell carcinoma: Nodular basal cell carcinoma is the most common type of skin cancer. This tumor usually resembles a smooth, round, waxy pimple, pale yellow or pearl gray, and may vary in size from a few millimeters to one centimeter. The skin covering the nodule is usually so thin that the slightest injury will cause it to bleed. These tumors are often depressed in the middle and display ulcerations. As the tumor grows, it destroys healthy structures in its path, including nerves, muscles, and blood vessels. Large tumors are easily diagnosed, but smaller ones are often difficult to tell from benign skin conditions, such as warts, seborrheic keratoses, moles, psoriasis, or fever sores. Other types of basal cell carcinomas include superficial, sclerosing, pigmented fibroepithelioma, basosquamous carcinoma, and basal cell nevus syndrome.
Melanoma: Moles, brown spots, and growths on the skin are usually harmless, but may increase the risk of developing melanoma, especially if there are more than 100 moles on the body. Diagnosis of melanoma will need to be made when moles appear to be asymmetric (if a line is drawn through the mole and the two halves don't match), have uneven borders, variety of colors (shades of brown, tan, or black), are large in size, or are changing. The type of melanoma will also be determined.
Once the type of melanoma has been established, the next step is to classify the disease as to its degree of severity. Melanoma, like other cancers, is classified in stages, and the stage will determine the treatment. Early melanomas (Stages I and II) are localized, and advanced melanomas (Stages III and IV) have spread to other parts of the body, or
metastasized. There are also degrees within stages.
Breslow's thickness: The most important factor in staging a melanoma is the thickness of the tumor, known as
Breslow's thickness, and the appearance of
ulcerations (sores). Breslow's thickness measures in millimeters the distance between the upper layer of the epidermis and the deepest point of the tumor's penetration. The thinner the melanoma, the better the chance of a cure. Breslow's thickness diagnoses include: in situ melanoma confined to the epidermis, very thin tumors of less than 1.0 millimeter, thin tumors of 1.01=2.0 mm, intermediate tumors of 2.0-4.0 mm, and thick melanomas of 4.00 mm or more. The presence of microscopic ulcerations moves the tumor into a later stage.
Clark's level of invasion: Very thin tumors are classified according to
Clark's level of invasion, which describes the number of layers of skin penetrated by the tumor. Clark's level I signifies the melanoma occupies only the epidermis. Clark's level II means that the melanoma penetrates to the layer immediately under the epidermis, the papillary dermis, Clark's level III means that the melanoma fills the papillary dermis and may touch the next layer known as reticular dermis, and Clark's level IV is when the melanoma penetrates into the reticular or deep dermis. Clark's level V melanoma invades the subcutaneous fat.
Stage I: This category is subdivided according to the thickness of the primary (original) tumor. In Stage 1a, the tumor is less than 1.0 mm in Breslow's thickness without ulceration and is in Clark's level II or III. In Stage Ib, the
tumor is less than 1.0 mm in Breslow's thickness with ulceration and/or Clark's level III or IV, or it is 1.01 - 2.0 mm in thickness without ulceration.
Stage II: This category is also subdivided according to gradations in thickness and/or depth and the presence or absence of ulceration. In Stage IIa, the tumor is 1.01 - 2.0 mm in Breslow's thickness with ulceration, or is 2.01-4.0 mm in thickness without ulceration. In Stage IIb, the tumor is 2.01-4.0 mm in Breslow's thickness with ulceration, or is greater than 4.0 mm in thickness without ulceration. In Stage I?c, the tumor is greater than 4.0 mm in Breslow's thickness with ulceration.
Stage III: When a melanoma is in Stage III or greater, the tumor has either spread to the lymph nodes or to the skin between the primary tumor and the nearby lymph nodes. This can be determined by examining a biopsy of the node nearest the tumor, known as the sentinel node. Such a biopsy is now frequently done when a tumor is more than 1 mm in thickness, or when a thinner melanoma shows evidence of ulceration. In Stage III, the metastasis (spreading) is to the skin or underlying tissue (subcutaneous) for a distance of more than 2 centimeters (1 cm equals 0.4 inch) from the primary tumor, but not beyond the regional lymph nodes. These metastases are microscopic.
Stage IV: Stage IV melanoma has metastasized to lymph nodes far away from the primary tumor or to internal organs, most often the lung followed in descending order of frequency by the liver, brain, bone, and gastrointestinal tract.
signs and symptoms
Skin cancer develops primarily on areas of sun-exposed skin, including the scalp, face, lips, ears, neck, chest, arms, hands, and on the legs in women. It also can form on areas not receiving as much light such as the palms, spaces between the toes, and the genital area.
A cancerous skin lesion can appear suddenly or develop slowly, it depends on the type of cancer.
Basal Cell Carcinoma: Basal cell carcinoma may appear as a flat, scaly red patch, a pearly or waxy bump on the face, ears, or neck (bumps may bleed or develop a crust), a patch with large blood vessels (may look like a birthmark), or a brown or black raised bump.
Squamous Cell Carcinoma: Squamous cell carcinoma may appear as a flat, scaly red patch (may look similar to a skin rash), a small, smooth, shiny, or waxy bump, a firm, red nodule on the face, lips, ears, neck, hands or arms, or a red or brown, scaly skin patch.
Malignant Melanoma: Although it can occur anywhere on the body, melanoma appears most often on the upper back or face in both men and women. Malignant melanoma may appear as a new mole, a mole that has gotten larger, a mole that changes color or shape, a mole that bleeds, a mole that itches or causes pain, or a mole with an uneven border or shape. Warning signs of melanoma include a large brownish spot with darker speckles located anywhere on the body, a simple mole located anywhere on the body that changes color, size, feel or that bleeds, or a small lesion with an irregular border and red, white, blue, or blue-black spots on the trunk or limbs. Other signs include shiny, firm, dome-shaped bumps located anywhere on the body and dark lesions on the palms, soles, fingertips and toes, or on mucous membranes lining the mouth, nose, vagina and anus.
Superficial spreading melanoma: This type of melanoma is the most common type, accounting for about 70% of all cases. Superficial spreading melanoma travels along the top layer of the skin for a fairly long time before penetrating more deeply. It is most common in younger people. The melanoma appears as a flat or slightly raised discolored patch that has irregular borders and is somewhat geometrical in form, with various colors (tan, brown, black, red, blue or white) in it. The melanoma can be found almost anywhere on the body, but is most likely to occur on the trunk in men, the legs in women, and the upper back in both. Other forms of melanoma include lentigo maligna, acral lentiginous melanoma, and nodular melanoma.
Kaposi's sarcoma: Kaposi's sarcoma is a rare form of skin cancer that develops in the skin's blood vessels and causes red or purple patches on the skin or mucous membranes. Like melanoma, it's a serious form of skin cancer. This form of skin cancer is mainly seen in people with weakened immune systems, such as people with AIDS or taking medications that suppress their immunity (immunosuppressive medications in transplant patients).
Merkel cell carcinoma: Merkel cell carcinoma is a rare cancer that appears as firm, shiny nodules occurring on or just beneath the skin and in hair follicles. The nodules may be red, pink, or blue and can vary in size from a quarter of an inch to more than two inches. Merkel cell carcinoma is usually found on sun-exposed areas of the head, neck, arms, and legs. Unlike basal and squamous cell carcinomas, merkel cell carcinoma grows rapidly and often spreads to other parts of the body.
Sebaceous gland carcinoma: Sebaceous gland carcinoma is an uncommon and aggressive form of skin cancer. This form of skin cancer originates in the oil producing glands in the skin. It usually appears as hard, painless nodules that can develop anywhere, but occurs most on the eyelids where they're frequently mistaken for benign conditions.
Precancerous skin lesions: Precancerous skin lesions, including actinic keratosis, can also develop into squamous cell skin cancer. Actinic keratoses appear as rough, scaly, brown or dark-pink patches. They're most commonly found on the face, ears, lower arms and hands of fair-skinned people whose skin has been damaged by the sun. Other precancerous skin lesions include actinic cheilitis (in the lips), arsenical keratosis (exposure to arsenic), Bowen's Disease (superficial SCC that hasn't spread), and leukoplakia (disease of the mucous membrane).
Scarring: Some complications of skin cancer can be scars and disfigurement, but it is not usually life-threatening.
Metastasis: Once a melanoma is diagnosed past Stage III, metastasis may be found increasing the complications for the patient and treatment involved.
Recurrent skin cancer: Once there has been a diagnosis of skin cancer, a second tumor may be more likely.
Age: Older individuals have a higher risk of developing skin cancer, mainly because many skin cancers develop slowly. Damage by other risk factors that occurred during childhood or adolescence may not become apparent until middle age, but skin cancer can occur in all ages. Basal cell and squamous cell carcinomas are increasing rapidly among women younger than 40.
Environmental exposure: Exposure to harsh environmental chemicals, including arsenic, cosmetics, and some herbicides increases the risk of skin cancer.
Fair skin: The less pigment (melanin) the skin contains, the less protection from damaging UV radiation. People with blond or red hair, or light-colored eyes will freckle or sunburn more easily. These individuals are much more likely to develop skin cancer than a person with darker features.
Family history: Having a parent or a sibling who has developed skin cancer increases the risk of developing skin cancer. Some families are affected by a condition called familial atypical multiple mole melanoma (FAMMM) syndrome. The hallmarks of FAMMM include a history of melanoma in one or more close relatives and having more than 50 moles, some of which are atypical. Because people with this syndrome have an extremely high risk of developing melanoma, frequent screening for signs of skin cancer is crucial.
Fragile skin: If the skin is burned, injured, or weakened by treatments for other skin conditions, it is more susceptible to sun damage and skin cancer development.
Moles: Having lots of moles or abnormal moles (called dysplastic nevi) increases the risk of developing skin cancer. The abnormal moles are irregular and generally larger than normal moles, and are more likely than others to become cancerous.
Personal history: If an individual has developed skin cancer in the past, their risk for developing the disease again is increased. Even basal cell and squamous cell carcinomas that have been successfully removed can recur in the same spot, often within two to three years.
Precancerous skin lesions: Skin lesions known as actinic keratoses can increase the risk of developing skin cancer. These precancerous skin growths typically appear as rough, scaly patches that range in color from brown to dark pink. Actinic keratoses are most common on the face, lower arms and hands of fair-skinned people whose skin has been sun damaged.
Sun Exposure: Individuals who spend a considerable amount of time in the sun can develop skin cancer, especially if the skin isn't protected by sunscreen or clothing. Tanning is the skin's injury response to excessive UV radiation, and increases the risk of skin cancer.
Sunburn: Sunburn is the body's attempt to heal itself from the sun's damaging rays. Every time an individual gets sunburned, there is an increased risk of damaging skin cells and developing skin cancer. One or more severe, blistering sunburns can increase the risk of skin cancer as an adult.
Sunny or high-altitude climates: Individuals living in sunny, warm climates are exposed to more sunlight than those in colder climates. Higher elevations make UV rays stronger, and may also increase the risk of developing skin cancer.
Weak immune system: Individuals with weakened immunities are at a greater risk for developing skin cancer. This includes people living with HIV/AIDS, leukemia, and those taking immunosuppressant drugs after an organ transplant.