Doctor's Notes on Skin Cancer
Skin cancer is the most common of all human cancers. There are three major types of skin cancers: basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. Most skin cancers are BCCs or SCCs which may be locally disfiguring if not treated early, but they usually do not spread to other parts of the body. A small number of skin cancers are malignant melanomas, which are highly aggressive and tend to spread (metastasize) to other parts of the body. Melanomas can be fatal if not diagnosed and treated promptly.
Symptoms of basal cell carcinoma (BCC) skin cancer include a raised, smooth, pearly bump on the sun-exposed skin of the head, neck, or shoulders. Small blood vessels may be visible within the tumor and a central depression with crusting and bleeding is common. It may be mistaken for a sore that does not heal. Symptoms of squamous cell carcinoma (SCC) skin cancer include a well-defined, red, scaling, thickened patch on sun-exposed skin that may ulcerate and bleed. If not treated, untreated, squamous cell carcinoma may develop into a large mass. Symptoms of malignant melanoma skin cancer include brown to black pigmented lesions. Warning signs that are indicative of malignant melanoma include changes in size, shape, color, or elevation of a mole; new mole that develops during adulthood; or new pain, itching, ulceration, or bleeding of an existing mole.
Skin Cancer Symptoms
A basal cell carcinoma (BCC) usually looks like a raised, smooth, pearly bump on the sun-exposed skin of the head, neck, or shoulders.
- Small blood vessels may be visible within the tumor.
- A central depression with crusting and bleeding (ulceration) frequently develops.
- A BCC is often mistaken for a sore that does not heal.
A squamous cell carcinoma (SCC) is commonly a well-defined, red, scaling, thickened patch on sun-exposed skin.
- Like BCCs, SCCs may ulcerate and bleed.
- Left untreated, SCC may develop into a large mass.
The majority of malignant melanomas are brown to black pigmented lesions.
- Warning signs include change in size, shape, color, or elevation of a mole.
- The appearance of a new mole during adulthood, or new pain, itching, ulceration, or bleeding of an existing mole should all be checked by a healthcare professional.
The following easy-to-remember guideline, "ABCD," is useful for identifying malignant melanoma:
- Asymmetry-One side of the lesion does not look like the other.
- Border irregularity-Margins may be notched or irregular.
- Color-Melanomas are often a mixture of black, tan, brown, blue, red, or white.
- Diameter-Cancerous lesions are usually larger than 6 mm across (about the size of a pencil eraser), but any change in size may be significant.
Skin Cancer Causes
Ultraviolet (UV) light exposure, most commonly from sunlight, is overwhelmingly the most frequent cause of skin cancer.
Other important causes of skin cancer include the following:
- Use of tanning booths
- Immunosuppression - This means impairment of the immune system. The immune system protects the body from foreign entities, such as germs or substances that cause an allergic reaction. This suppression may occur as a consequence of some diseases or can be due to medications prescribed to combat conditions such as autoimmune diseases or prevent organ transplant rejection.
- Exposure to unusually high levels of X-rays
- Contact with certain chemicals-arsenic (miners, sheep shearers, and farmers), hydrocarbons in tar, oils, and soot (may cause squamous cell carcinoma)
The following people are at the greatest risk:
- People with fair skin, especially types that freckle, sunburn easily, or become painful in the sun
- People with light (blond or red) hair and blue or green eyes
- Those with certain genetic disorders that deplete skin pigment such as albinism, xeroderma pigmentosum
- People who have already been treated for skin cancer
- People with numerous moles, unusual moles, or large moles that were present at birth
- People with close family members who have developed skin cancer
- People who had at least one severe sunburn early in life
Basal cell carcinomas and squamous cell carcinomas are more common in older people. Melanomas can occur at any age. It is most commonly diagnosed at between 55 and 75 years of age, but about 1/3 occur before the age of 50. For example, melanoma is the most common cancer in people younger than 30.
Sunlight contains ultraviolet light that is harmful to human skin cells. These energetic light waves can produce mutations in the DNA of skin cells, which in turn can lead to skin cancer. In areas close to the equator, the incidence of cutaneous cancers is dramatically higher due to the increase in sun exposure.
The most obvious skin cancer warning sign is the development of a persistent bump or spot in an area of sun-damaged skin. These spots are likely to bleed with minimal trauma and produce a superficial erosion.
Ultraviolet Light and Skin Cancer
Ultraviolet rays are classified by three types: UVA, UVB, and UVC. UVC is very dangerous, but it does not reach the earth’s surface due to the ozone layer. Exposure to both UVA and UVB radiation poses potential skin cancer risks.
UVA light is the most abundant source of solar radiation. Scientists think it can penetrate the top layer of skin, potentially damaging connective tissue and causing skin cancer. An estimated 50% of UVA exposure occurs in the shade. Light skin is far more vulnerable to UVA radiation: while dark skin allows only 17.5% of UVA to penetrate, light skin allows 55% of UVA light to pass through.
Sunburns are mostly caused by UVB radiation. Because of the ozone layer, UVB light accounts for only about 5% of the light that reaches the earth’s surface. UVB light can be filtered out by glass windows and does not penetrate as far into the skin as UVA, but it can still cause some forms of skin cancer. UVB is absorbed directly by DNA. Dark skin is twice as effective as light skin at protecting against UVB penetration.
How Skin Cancer Develops
UV light causes skin cancer by damaging the skin’s cellular DNA. That damage is caused by free radicals, which are hyperactive molecules found in UV light. Free radicals cause damage to the DNA double helix, changing the way cells replicate and naturally die, which is how cancer develops. In addition to sun exposure, free radicals are also found in environmental pollutants, cigarette smoke, alcohol, and other toxins.
Melanoma (Skin Cancer) : Symptoms & Signs QuizQuestion
Self-examination is important in the detection of skin cancer.See Answer
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.