SKIN CANCER DEFINITION
Skin cancer — the abnormal growth of skin cells — most often develops on skin exposed to the sun. But this common form of cancer can also occur on areas of your skin not ordinarily exposed to sunlight.
There are three major types of skin cancer — basal cell carcinoma, squamous cell carcinoma and melanoma.
You can reduce your risk of skin cancer by limiting or avoiding exposure to ultraviolet (UV) radiation. Checking your skin for suspicious changes can help detect skin cancer at its earliest stages. Early detection of skin cancer gives you the greatest chance for successful skin cancer treatment.
SKIN CANCER CAUSES
Most skin cancers are caused by exposure to the sun. This may be long term exposure, or short periods of intense sun exposure and burning. Look at the preventing skin cancer page in this section for lots of information about how to protect your skin from the sun.
The ultraviolet light in sunlight damages the DNA in the skin cells. This damage can happen years before a cancer develops. The sun’s rays contain 3 types of ultraviolet light.
- UVA makes up most of our natural sun light. It goes deeper into the skin and causes skin ageing. It is now also linked to skin cancer
- UVB is most likely to burn the skin and is the main cause of non-melanoma skin cancer
- UVC is filtered out by the atmosphere of the earth (ozone layer)
SKIN CANCER PATHOPHYSIOLOGY
The sequence of events in which normal melanocytes transform into melanoma cells, referred to as melanomagenesis, is poorly understood. It likely involves a multistep process of progressive genetic mutations that (1) alter cell proliferation, differentiation, and death and (2) impact susceptibility to the carcinogenic effects of ultraviolet radiation.Recent data suggest multiple pathways of melanoma pathogenesis, with melanomas in sun-protected skin (trunk) developing in association with a high nevus count and intermittent ultraviolet radiation as opposed to those developing on sun-exposed skin in patients with low nevus counts and chronic sun exposure.
Differences in frequency of BRAF or NRAS mutations are also related to patterns of sun exposure, with BRAF mutations more common in intermittently UV-exposed skin compared with chronically sun exposed skin or relatively unexposed skin (eg, acral sites, mucosal sites), which more frequently demonstrate KIT mutations.
A meta-analysis by Lee et al demonstrated that the prevalence of these mutations may also depend on melanoma histologic subtype.
Primary cutaneous melanoma may develop in precursor melanocytic nevi (ie, common, congenital, and atypical/dysplastic types), although more than 70% of cases are believed to arise de novo (ie, not from a preexisting pigmented lesion).
The development of melanoma is multifactorial and appears to be related to multiple risk factors, including fair complexion/sun sensitivity, excessive childhood sun exposure and blistering childhood sunburns, an increased number of common or atypical/dysplastic nevi (moles), a family history of melanoma, the presence of a changing mole or evolving lesion on the skin, and, importantly, older age.
SKIN CANCER SYMPTOMS
Skin cancer develops primarily on areas of sun-exposed skin, including the scalp, face, lips, ears, neck, chest, arms and hands, and on the legs in women. But it can also form on areas that rarely see the light of day — your palms, beneath your fingernails or toenails, and your genital area.
Skin cancer affects people of all skin tones, including those with darker complexions. When melanoma occurs in people with dark skin tones, it’s more likely to occur in areas not normally exposed to the sun, such as the palms of the hands and soles of the feet.
Basal cell carcinoma signs and symptoms
Basal cell carcinoma usually occurs in sun-exposed areas of your body, such as your neck or face.
Basal cell carcinoma may appear as:
- A pearly or waxy bump
- A flat, flesh-colored or brown scar-like lesion
Squamous cell carcinoma signs and symptoms
Most often, squamous cell carcinoma occurs on sun-exposed areas of your body, such as your face, ears and hands. People with darker skin are more likely to develop squamous cell carcinoma on areas that aren’t often exposed to the sun.
Squamous cell carcinoma may appear as:
- A firm, red nodule
- A flat lesion with a scaly, crusted surface
Melanoma signs and symptoms
Melanoma can develop anywhere on your body, in otherwise normal skin or in an existing mole that becomes cancerous. Melanoma most often appears on the face or the trunk of affected men. In women, this type of cancer most often develops on the lower legs. In both men and women, melanoma can occur on skin that hasn’t been exposed to the sun.
Melanoma can affect people of any skin tone. In people with darker skin tones, melanoma tends to occur on the palms or soles, or under the fingernails or toenails.
Melanoma signs include:
- A large brownish spot with darker speckles
- A mole that changes in color, size or feel or that bleeds
- A small lesion with an irregular border and portions that appear red, white, blue or blue-black
- Dark lesions on your palms, soles, fingertips or toes, or on mucous membranes lining your mouth, nose, vagina or anus
Signs and symptoms of less common skin cancers
Other, less common types of skin cancer include:
- Kaposi sarcoma. This rare form of skin cancer develops in the skin’s blood vessels and causes red or purple patches on the skin or mucous membranes.
Kaposi sarcoma mainly occurs in people with weakened immune systems, such as people with AIDS, and in people taking medications that suppress their natural immunity, such as people who’ve undergone organ transplants.
Other people with an increased risk of Kaposi sarcoma include young men living in Africa or older men of Italian or Eastern European Jewish heritage.
- Merkel cell carcinoma. Merkel cell carcinoma causes firm, shiny nodules that occur on or just beneath the skin and in hair follicles. Merkel cell carcinoma is most often found on the head, neck and trunk.
- Sebaceous gland carcinoma. This uncommon and aggressive cancer originates in the oil glands in the skin. Sebaceous gland carcinomas — which usually appear as hard, painless nodules — can develop anywhere, but most occur on the eyelid, where they’re frequently mistaken for other eyelid problems.
SKIN CANCER DIAGNOSIS
Skin cancer is diagnosed by physical examination and biopsy.
Biopsy is a quick and simple procedure where part or all of the spot is removed and sent to a laboratory. It may be done by your family doctor or you can be referred to a dermatologist or surgeon. Results may take about a week to be ready.
SKIN CANCER TREATMENT
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.