Overview of skin cancer
Skin cancer is the kind of cancer that forms in tissues of the skin. Most skin cancers form in older people on parts of the body exposed to the sun or in people who have weakened immune systems.1 Skin cancer is divided into melanoma and nonmelanoma skin cancer (NMSC).2
Skin cancer that forms in melanocytes of the outer layer of the skin or the epidermis (skin cells that make pigment). These include several subtypes, including the following:3
- Lentigo maligna melanoma, arising on sun-exposed skin of older individuals.
- Superficial spreading malignant melanoma is the most common type and it occurs in two-thirds of individuals.
- Nodular malignant melanoma.
- Acral-lentiginous melanomas, arising on palms, soles and nail beds).
- Malignant melanomas on mucous membranes.
- Miscellaneous forms such as amelanotic (nonpigmented) melanoma and melanomas arising from blue nevi (rare) and congenital nevi.
Nonmelanoma Skin Cancer
This is also known as keratinocyte carcinoma or keratinocyte cancer because the cells resemble keratinocytes (the cells found most often in normal skin). This includes the following two types of cancer.
- Basal cell carcinoma: Skin cancer that forms in basal cells (small, round cells in the base of the outer layer of skin).
- Squamous cell carcinoma: Skin cancer that forms in squamous cells (flat cells that form the surface of the skin).
While NMSCs are more common and have better prognosis, melanoma is a rare form of skin cancer and is associated with a poor prognosis.
Signs and Symptoms of skin cancer
The symptoms of skin cancer depend on the type of skin cancer.
The major clinical features of melanoma are described below.3
- Majority are brown to black pigmented lesions.
- Melanomas vary from macules to nodules.
- There can be a variation in color from flesh tints to pitch black and a frequent admixture of white, blue, purple, and red may occur.
- The border tends to be irregular, and growth may be rapid or indolent.
- Melanomas are often larger than 6 mm.
- 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 be checked by a physician.
Basal Cell Carcinoma
Basal cell carcinomas grow slowly, attaining a size of 1–2 cm or more in diameter, often after years of growth.4
Usually a raised, smooth, pearly bump on the sun-exposed skin of the head, neck or shoulders.
- The most common presentation is a papule or nodule that may have a central scab or erosion.
- Occasionally the nodules have stippled pigment.
- There is a waxy, “pearly” appearance, with small blood vessels, which are easily visible. It is the pearly or translucent quality of these lesions that is most diagnostic, a feature best appreciated if the skin is stretched.
- Less common types include morpheaform or scar-like lesions. These are hypopigmented, somewhat thickened plaques.
- On the back and chest, basal cell carcinomas appear as reddish, somewhat shiny, scaly plaques.
Commonly a well-defined red, scaling, thickened patch on sun-exposed skin.
Squamous Cell Carcinoma
The lesions appear as small red, conical, hard nodules that occasionally ulcerate. If left untreated, this carcinoma may develop into a large mass.5
Risk Factors for skin cancer
All forms of skin cancer are showing an increasing incidence rate worldwide.
Majority of all melanoma cases are caused, at least partially, by excessive exposure to sunlight. In contrast to squamous cell carcinoma, melanoma risk seems not to be associated with cumulative, but intermittent exposure to sunlight. Cutaneous malignant melanoma is the most rapidly increasing cancer in white populations. The frequency of its occurrence is closely associated with the constitutive color of the skin and depends on the geographical zone.2
The broad grounds for relating sun exposure to skin cancer had been established by 1927 for NMSCs and by 1955 for melanoma. The past 40 years have added both quantity and quality to the epidemiological evidence and, most recently, provided direct evidence that sun exposure is the cause of mutations in critical tumor suppressor genes in both these cancers.6
Nonmelanoma Skin Cancer
The rising incidence rates of NMSC are probably caused by the following:2
- A combination of increased sun exposure or exposure to ultraviolet (UV) light,
- Increased outdoor activities.
- Changes in clothing style.
- Increased longevity
- Ozone depletion, genetics.
- In some cases, immune suppression.2
Diagnosis of skin cancer
In case there is a change on the skin, it is important to find out whether it is due to cancer or to some other cause. A biopsy is done for this purpose. A biopsy is the only sure way to diagnose skin cancer.7
There are four common types of skin biopsies:
Punch biopsy: The doctor uses a sharp, hollow tool to remove a circle of tissue from the abnormal area.
Incisional biopsy: The doctor uses a scalpel to remove part of the growth.
Excisional biopsy: The doctor uses a scalpel to remove the entire growth and some tissue around it.
Shave biopsy: The doctor uses a thin, sharp blade to shave off the abnormal growth.
Treatment of skin cancer
Treatment for skin cancer and the precancerous skin lesions known as actinic keratoses varies, depending on the size, type, depth and location of the lesions. Often, the abnormal cells are surgically removed or destroyed with topical medications. Most skin cancer treatments require only a local anesthetic and can be done in an outpatient setting. Sometimes no treatment is necessary beyond an initial biopsy that removes the entire growth.
In case additional treatment is required, following are the various options:
Freezing: Actinic keratoses and some small, early skin cancers are destroyed by freezing them with liquid nitrogen (cryosurgery). The dead tissue sloughs off when it thaws. The treatment may leave a small, white scar. A repeat treatment may be required to remove the growth completely.
Excisional surgery: This type of treatment may be appropriate for any type of skin cancer. The cancerous tissue and a surrounding margin of healthy skin are removed. A wide excision, where extra normal skin around the tumor is removed. This therapy may be recommended in some cases.
Laser therapy: A precise, intense beam of light vaporizes growths, generally with little damage to surrounding tissue and with minimal bleeding, swelling and scarring. This therapy may be used to treat superficial skin cancers or precancerous growths on lips.
Mohs surgery: This procedure is for larger, recurring or difficult-to-treat skin cancers, which may include both basal and squamous cell carcinomas. The skin growth layer by layer is removed, examining each layer under the microscope, until no abnormal cells remain. This procedure allows cancerous cells to be removed without taking an excessive amount of surrounding healthy skin.
Curettage and electrodessication: After removing most of a growth, layers of cancer cells are scrapped away using a circular blade (curet). An electric needle destroys any remaining cancer cells. This simple, quick procedure is common in treating small or thin basal cell cancers. It leaves a small, flat, white scar.
Radiation therapy: Radiation may be used to destroy basal and squamous cell carcinomas if surgery is not an option.
Chemotherapy: Here, drugs are used to kill cancer cells. For cancers limited to the top layer of skin, creams or lotions containing anticancer agents may be applied directly to the skin. Topical drugs can cause severe inflammation and leave scars. Systemic chemotherapy can be used to treat skin cancers that have spread to other parts of the body.
Prevention of skin cancer
Primary prevention of skin cancer is by increasing public awareness of the risks of sun exposure and providing patients with individualized guidance. Patients who are educated about risk factors for skin cancer are more likely to self-select for clinical screening and to bring malignant lesions to the attention of a healthcare provider.8,9 Gloster et al. describe the ‘safe sun’ guidelines for the prevention of skin cancer (see Box 1).10
‘Safe Sun’ Guidelines for the Prevention of Skin Cancer
- Sun exposure during the peak UVB hours should be avoided or minimized. The peak UVB period is from 10 am to 4 pm.
- Sunscreen with a solar protection factor of at least 15 (Query: what is 15? Pl check) should be generously applied.
- In addition to use of an appropriate sunscreen, people should wear wide-brimmed hats, sunglasses and protective clothing (e.g., tightly woven fabrics and long-sleeved shirts) when sun exposure during peak UVB hours cannot be avoided.
- Deliberate sun tanning and use of tanning parlors should be avoided.
Most evidence suggests that the correct use of sunscreens can lower the risk of skin cancer.11 Sufficient amounts must be applied at least 30 min before sun exposure with reapplication after prolonged exposure or swimming. Most importantly, sunscreens are not effective unless they are employed as only one element of a skin cancer prevention program.
1. National Cancer Institute. US National Institutes of Health. Skin Cancer. Available at: http://www.cancer.gov/cancertopics/types/skin. Accessed on: 17June 08.
2. Leiter U, Garbe C. Epidemiology of melanoma and nonmelanoma skin cancer—The role of sunlight. Adv Exp Med Biol. 2008; 624: 89–103.
3. Tierney LM Jr., McPhee SJ, Papadakis MA (eds). Malignant melanoma. In: Current Medical Diagnosis and Treatment.. 2005; pp. 92–93.
4. Tierney LM Jr., McPhee SJ, Papadakis MA (eds). Basal cell carcinoma. In: Current Medical Diagnosis and Treatment. 2005; pp. 127–128.
5. Tierney LM Jr., McPhee SJ, Papadakis MA (eds). Squamous cell carcinoma. In: Current Medical Diagnosis and Treatment. 2005; pp. 128–129.
6. Armstrong BK, Kricker A, English DR. Sun exposure and skin cancer. Australas J Dermatol. 1997 38(Suppl 1): S1–S6.
7. National Cancer Institute. US National Institutes of Health. What you need to know about skin cancer. Available at: http://www.cancer.gov/cancertopics/wyntk/skin/page7. Accessed on: 17 June 08.
8. Rivers JK, Gallagher RP. Public education projects in skin cancer. Experience of the Canadian Dermatology Association. Cancer. 1995; 75: 661–666.
9. Jones TP, Boiko PE, Piepkorn MW. Skin biopsy indications in primary care practice: A population-based study. J Am Board Fam Pract. 1996; 9: 397–404.
10. Gloster HM, Brodland DG. The epidemiology of skin cancer. Dermatol Surg. 1996; 22: 217–226.
11. Naylor MF, Farmer KC. The case for sunscreens. A review of their use in preventing actinic damage and neoplasia. Arch Dermatol. 1997; 133: 1146–1154.
Written by: healthplus24.com team
Date last updated: February 02, 2015