Skin cancer is a common and locally destructive cancerous (malignant) growth of the skin. It originates from the cells that line up along the membrane that separates the superficial layer of skin from the deeper layers. Unlike cutaneous malignant melanoma, the vast majority of these sorts of skin cancers have a limited potential to spread to other parts of the body (metastasize) and become life-threatening.
Skin cancer, including both malignant melanoma (MM) and non-melanoma skin cancer (NMSC), represents the most common malignancy in Caucasians. The incidence of both MM and NMSC is on the rise, with an annual increase in MM of 0.6% among adults over 50 years. The estimated number of new cases of skin melanoma in 2016 is 76,380, which represents 4.5% of all new cancer cases. Deviations in reported incidence rates exist and are attributed to varying risk factors amongst different populations, as well as discrepancies in national registration systems. Furthermore, the incidence of melanoma may be even higher than indicated, as the National Cancer Registries has reported an underestimation of its incidence in certain countries
Types of skin cancer
Actinic Keratoses (AK)
These dry, scaly patches or spots are precancerous growths.
- People who get AKs usually have fair skin.
- Most people see their first AKs after 40 years of age because AKs tend to develop after years of sun exposure.
- AKs usually form on the skin that gets lots of sun exposure, such as the head, neck, hands, and forearms.
- Because an AK can progress to a type of skin cancer called squamous cell carcinoma (SCC), treatment is important.
Basal cell carcinoma (BCC)
This is the most common type of skin cancer.
- BCCs frequently develop in people who have fair skin, yet they can occur in people with darker skin.
- BCCs look like a flesh-colored, pearl-like bump or a pinkish patch of skin.
- BCCs develop after years of frequent sun exposure or indoor tanning.
- BCC are common on the head, neck, and arms, yet can form anywhere on the body, including the chest, abdomen, and legs.
- Early diagnosis and treatment for BCC is important. BCC can invade the surrounding tissue and grow into the nerves and bones, causing damage and disfigurement.
Squamous cell carcinoma (SCC)
SCC is the second most common type of skin cancer.
- People who have light skin are most likely to develop SCC, yet they can develop in darker-skinned people.
- SCC often looks like a red firm bump, scaly patch, or a sore that heals and then re-opens.
- SCC tend to form on skin that gets frequent sun exposure, such as the rim of the ear, face, neck, arms, chest, and back. SCC can grow deep in the skin and cause damage and disfigurement. Early diagnosis and treatment can prevent this and stop SCC from spreading to other areas of the body.
Melanoma is the deadliest form of skin cancer.
- Melanoma frequently develops in a mole or suddenly appears as a new dark spot on the skin.
- Early diagnosis and treatment are crucial.
- Knowing the asymmetry, border, color, diameter and evolving (ABCDE) warning signs of melanoma can help you find an early melanoma.
Risk factors of skin cancer
The most common risk factors for skin cancer are as follows.
- Ultraviolet light exposure, either from the sun or from tanning beds. Fair-skinned individuals, with hazel or blue eyes, and people with blond or red hair are particularly vulnerable. The problem is worse in areas of high elevation or near the equator where sunlight exposure is more intense.
- A chronically suppressed immune system (immunosuppression) from underlying diseases such as HIV/AIDS infection or cancer, or from some medications such as prednisone or chemotherapy
- Exposure to ionizing radiation (X-rays) or chemicals known to predispose to cancer such as arsenic
- Certain types of sexually acquired wart virus infections
- People who have a history of one skin cancer have a 20% chance of developing a second skin cancer in the next two years.
- Elderly patients have more skin cancers.
Causes of skin cancer
The majority of skin cancer is caused by overexposure to ultraviolet (UV) radiation from the sun and artificial sources such as solariums. UV radiation is strong enough to damage skin cells and cause skin cancer.
- Sunlight is made up of light, heat and ultraviolet (UV) radiation. Visible rays of the sun are light-giving rays, while infrared rays provide heat.
- UV radiation is the part of sunlight that causes sunburn and skin damage and leads to premature ageing and skin cancer. There are three types of naturally occurring ultraviolet rays – UVA, UVB and UVC.
- UVA radiation penetrates deep into the skin, affecting the living skin cells that lie under your skin’s surface. UVA causes long-term damage like wrinkles, blotchiness, sagging and discoloration, and also contributes to skin cancer.
- UVB radiation penetrates the top layer of skin and is the cause of skin tanning, sunburn, and skin cancer.
- UVA and UVB are of concern because of their potential to cause skin cancer.
- UVC does not reach the earth’s surface and is absorbed or scattered in the atmosphere.
Signs and Symptoms of Skin Cancer
Both basal cell and squamous cell cancers can appear in a variety of forms. They are usually painless and grow slowly. They can show up anywhere on your body but are most likely to appear on exposed skin, especially on your face or neck.
Symptoms of basal cell carcinoma
Basal cell cancers may:
- Be smooth and pearly
- Look waxy
- Appear as a firm, red lump
- Bleed sometimes
- Develop a crust or scab
- Begin to heal but never completely heal
- Be itchy
- Look like a flat, red spot which is scaly and crusty
- Develop into a painless ulcer.
Symptoms of squamous cell carcinoma
Squamous cell cancers usually develop in areas that have been damaged by sun exposure. They are mainly found on the face, neck, bald scalps, arms, backs of hands and lower legs. Squamous cell cancers may:
- Look scaly
- Have a hard, horny cap
- Make the skin raised in the area of the cancer
- Feel tender to touch
- Bleed sometimes.
Diagnosis and test
To diagnose skin cancer, your doctor may:
Examine your skin: Your doctor may look at your skin to determine whether your skin changes are likely to be skin cancer. Further testing may be needed to confirm that diagnosis.
Remove a sample of suspicious skin for testing (skin biopsy): Your doctor may remove the suspicious-looking skin for lab testing. A biopsy can determine whether you have skin cancer and, if so, what type of skin cancer you have.
Determining the extent of the skin cancer
If your doctor determines you have skin cancer, you may have additional tests to determine the extent (stage) of the skin cancer.
- Because superficial skin cancers such as basal cell carcinoma rarely spread, a biopsy which removes the entire growth often is the only test needed to determine the cancer stage. But if you have a large squamous cell carcinoma, Merkel cell carcinoma or melanoma, your doctor may recommend further tests to determine the extent of the cancer.
- Additional tests might include imaging tests to examine the nearby lymph nodes for signs of cancer or a procedure to remove a nearby lymph node and test it for signs of cancer (sentinel lymph node biopsy).
- Doctors use the Roman numerals I through IV to indicate a cancer’s stage. Stage I cancers are small and limited to the area where they began. Stage IV indicates advanced cancer that has spread to other areas of the body.
- The skin cancer’s stage helps determine which treatment options will be most effective.
Treatment and medications
- Using a scalpel or curette (a sharp, ring-shaped instrument), a physician trained in Mohs surgery removes the visible tumor with a very thin layer of tissue around it. While the patient waits, this layer is sectioned, frozen, stained and mapped in detail, then checked under a microscope thoroughly.
- If cancer is still present in the depths or peripheries of this excised surrounding tissue, the procedure is repeated on the corresponding area of the body still containing tumor cells until the last layer viewed under the microscope is cancer free.
- Mohs surgery spares the greatest amount of healthy tissue, reduces the rate of local recurrence, and has the highest overall cure rate about 94-99 percent of any treatment for SCC. It is often used on tumors that have recurred, are poorly demarcated, or are in hard-to-treat, critical areas around the eyes, nose, lips, ears, neck, hands and feet.
- After tumor removal, the wound may be allowed to heal naturally or may be reconstructed immediately; the cosmetic outcome is usually excellent.
- The physician uses a scalpel to remove the entire growth, along with a surrounding border of apparently normal skin as a safety margin. The wound around the surgical site is then closed with sutures (stitches).
- The excised tissue specimen is then sent to the laboratory for microscopic examination to verify that all cancerous cells have been removed. A repeat excision may be necessary on a subsequent occasion if evidence of skin cancer is found in the specimen.
- The accepted cure rate for primary tumors with this technique is about 92 percent. This rate drops to 77 percent for recurrent squamous cell carcinomas.
Curettage and electrodessication (electro surgery)
- This technique is usually reserved for small lesions. The growth is scraped off with a curette (an instrument with a sharp, ring-shaped tip), and burning heat produced by an electrocautery needle destroys residual tumor and controls bleeding.
- This procedure is typically repeated a few times, a deeper layer of tissue being scraped and burned each time to help ensure that no tumor cells remain.
- It can produce cure rates approaching those of surgical excision for superficially invasive squamous cell carcinomas without high-risk characteristics. However, it is not recommended for any invasive or aggressive SCCs, those in high-risk or difficult sites, such as the eyelids, genitalia, lips and ears, or other sites that would be left with cosmetically undesirable results, since the procedure leaves a sizable, hypopigmented scar.
- The physician destroys the tumor tissue by freezing it with liquid nitrogen, using a cotton-tipped applicator or spray device.
- There is no cutting or bleeding, and no anesthesia is required. The procedure may be repeated several times at the same session to help ensure destruction of all malignant cells.
- The growth becomes crusted and scabbed, and usually falls off within weeks. Redness, swelling, blistering and crusting can occur following treatment, and in dark-skinned patients, some pigment may be lost.
- Inexpensive and easy to administer, cryosurgery may be the treatment of choice for patients with bleeding disorders or intolerance to anesthesia. However, it has a lower overall cure rate than the surgical methods.
- Depending on the physician’s expertise, the 5-year cure rate can be quite high with selected, generally superficial squamous cell carcinoma; but cryosurgery is not often used today for invasive SCC because deeper portions of the tumor may be missed and because scar tissue at the cryotherapy site might obscure a recurrence.
- X-ray beams are directed at the tumor, with no need for cutting or anesthesia. Destruction of the tumor usually requires a series of treatments, administered several times a week for one to four weeks, or sometimes daily for one month.
- Cure rates range widely, from about 85 to 95 percent, since the technique does not provide precise control in identifying and removing residual cancer cells at the margins of the tumor.
- The technique can involve long-term cosmetic problems and radiation risks, as well as multiple visits. For these reasons, though this therapy limits damage to adjacent tissue, it is mainly used for tumors that are hard to treat surgically, as well as patients for whom surgery is not advised, such as the elderly or those in poor health.
- PDT can be especially useful for growths on the face and scalp. A chemical agent that reacts to light, such as topical 5-aminolevulinic acid (5-ALA) or methyl aminolevulinate (MAL), is applied to the growths at the physician’s office; it is taken up by the abnormal cells. Hours later, those medicated areas are activated by a strong light.
- The treatment selectively destroys squamous cell carcinomas while causing minimal damage to surrounding normal tissue. However, the treatment is not yet FDA-approved for squamous cell carcinoma, and while it may be effective with early, noninvasive tumors (e.g., Bowen’s disease), overall recurrence rates vary considerably (from 0 to 52 percent), so the technique is not currently recommended for invasive SCC.
- Redness and swelling are common side effects. After treatment, patients become locally photosensitive for 48 hours where the light-sensitizing agent was applied, and must avoid both outdoor and indoor light and be careful to use sun protection.
- This therapy is not yet FDA-approved for SCC, though it can be used for superficial lesions, with recurrence rates similar to those of PDT. The skin’s outer layer and variable amounts of deeper skin are removed using a carbon dioxide or erbium YAG laser.
- This method is bloodless, and gives the physician good control over the depth of tissue removed. It actually seals blood vessels as it cuts, making it useful for patients with bleeding disorders, and it is also sometimes used when other treatments have failed. But the risks of scarring and pigment loss are slightly greater than with other techniques.
- 5-fluorouracil (5-FU) and imiquimod, both FDA-approved for treatment of actinic keratoses and superficial basal cell carcinomas, are also being tested for the treatment of some superficial squamous cell carcinomas. Successful treatment of Bowen’s disease, a noninvasive SCC, has been reported.
- However, invasive SCC should not be treated with 5-FU. Some trials have shown that imiquimod may be effective with certain invasive SCCs, but it is not yet FDA-approved for this purpose. Imiquimod stimulates the immune system to produce interferon, a chemical that attacks cancerous and precancerous cells, while 5-FU is a topical form of chemotherapy that has a direct toxic effect on cancerous cells.
- Because most treatment options involve cutting, some scarring from the tumor removal should be expected. This is most often cosmetically acceptable with small cancers, but removal of a larger tumor often requires reconstructive surgery, involving a skin graft or flap to cover the defect. Mohs surgeons are trained in reconstructive surgery, so visit to a plastic surgeon is usually unnecessary.
Deciding which treatment you need
A team of doctors and other professionals discuss the best treatment and care for you. They’re called a multidisciplinary team (MDT). Your treatment depends on:
- The type of skin cancer
- How far it’s grown or spread
- Where the cancer is
- The stage of the cancer (if relevant)
Your doctor will discuss your treatment, its benefits and the possible side effects with you.
Prevention of skin cancer
Nothing can completely undo sun damage, although the skin can sometimes repair itself. So, it’s never too late to begin protecting yourself from the sun. Your skin does change with age for example, you sweat less and your skin can take longer to heal, but you can delay these changes by staying out of the sun. Follow these tips to help prevent skin cancer:
- Apply sunscreen with a sun protection factor (SPF) of 15 or greater 30 minutes before sun exposure and then every few hours thereafter.
- Select cosmetic products and contact lenses that offer UV protection.
- Wear sunglasses with total UV protection.
- Avoid direct sun exposure as much as possible during peak UV radiation hours between 10:00 a.m. and 3:00 p.m.
- Perform skin self-exams regularly to become familiar with existing growths and to notice any changes or new growths.
- Eighty percent of a person’s lifetime sun exposure is acquired before age 18. As a parent, be a good role model and foster skin cancer prevention habits in your child.