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What Is Skin Cancer?

Skin cancer is the most common type of cancer in the United States caused by abnormal stem cells that begin to grow out of control in the epidermis. There are three main types of skin cancer, Basal Cell Carcinoma (BCC), Squamous Cell Carcinoma (SCC), and melanoma. BCC and SCC are the most common forms of skin cancer and are highly treatable when caught early. Melanoma is less common but is considered more dangerous because it has a greater chance of metastasis or migrating to other parts of the body.

→ Learn more about melanoma

Skin cancer has two main causes, unprotected overexposure to the sun’s ultraviolet (UV) rays and artificial UV sources like tanning beds. The UV rays damage the DNA in the stem cells of the skin, making them susceptible to transformation into cancer. Skin cancer most commonly occurs in sun-exposed areas of the body, especially the head, neck, and arms.

According to the American Academy of Dermatology, 1 in 5 Americans will develop skin cancer in their lifetime and approximately 9,500 people in the U.S. are diagnosed with skin cancer every day. An estimated 3 million Americans are affected by BCC and SCC every year. Nonmelanoma skin cancer is more common among women than men, however, invasive melanoma is the fifth most common cancer for men (about 60,000 cases a year) and the sixth most common for women (about 40,000 cases a year). States like Colorado have mores cases of skin cancer due to the abundance of sun and high altitudes. Sun exposure is more intense and damaging at higher elevations. 

When detected and treated early skin cancer is highly curable. For example, the estimated five-year survival rate for patients who get treatment for localized melanoma is 99%.

What is Skin?

The skin is one of the largest organs of the body and the first line of protection against the outside world. The skin has many important functions including:

  • Providing mechanical support for the body. 
  • Helping to regulate body temperature in hot conditions. 
  • Producing an important nutrient called vitamin D when exposed to sunlight. 
  • Keeping an eye out for invading pathogens and other noxious agents and notifying the immune system when a breach happens and helping mount a response.  

The skin is made up of two parts, an outer part called the epidermis, and an inner part called the dermis. The epidermis is made up of a single basal layer closest to the dermis and several layers of maturing suprabasal cells that become flat squamous cells. The epidermis is made up of several types of cells. They all have different functions, but keratinocytes are the most abundant and critical for skin barrier function. Melanocytes on the other hand are less abundant, but produce melanin, the brownish pigment that gives skin its color and allows the skin to tan. Other cell types include hair follicle, oil and sweat gland, sensory and immune cells. The Dermis contains a lot of connective tissue and blood vessels. It contains cells like fibroblasts, fat, nerve, and immune cells that provide the necessary nutrients and support for the epidermis to function properly.

One of the incredible facts about the skin is that the epidermis renews itself about every one and a half months. It is the job of professional stem cells in the basal layer of the skin to make more skins cells. They are immature cells that can either make more of themselves or change as they are needed into the mature squamous cells. Stem cells can also be found in the hair follicles. These stem cells help in fixing damaged skin during wounding. Once a basal stem cell decides to become a squamous cell through a process called differentiation, it will continue to move up the skin until it reaches the very top of the epidermis and dies. These dead cells are eventually lost. Exfoliation helps speed up dead skin cell removal. Unlike the transient nature of squamous cells, the stem cells live in the epidermis for many years. Because of this, stem cells live long enough to accumulate changes that make them susceptible to becoming cancer. 

Why Come to CU Cancer Center for Skin Cancer

The CU Cancer Center is the only National Cancer Institute (NCI) Comprehensive Cancer Centers in Colorado. We have doctors who are providing top-notch, multidisciplinary, patient-centered care and treatment options not available at most other medical centers in the country.  

The CU Cancer Center is one of 31 leading cancer centers part of the National Comprehensive Cancer Network (NCCN) advisory panel. NCCN cancer centers are dedicated to patient care, research and education. The advisory panel establishes treatment guidelines that doctors all across the United States use as a reference.  

There are a number of skin cancer clinical trials and research studies currently being offered by CU Cancer Center members, giving patients many different treatment options. 

Types of Skin Cancer

Basal Cell Carcinoma is a type of skin cancer that can begin in stem cells of the basal layers and in hair follicle tissue. BCC occurs most often on sun-exposed areas of the skin like the face, head, and neck and usually appears as a raised, pearly white, skin-colored, or pink bump on the skin. BCC are the most common type of skin cancer with a diagnosis rate of about 8 out of 10 skin cancers. This type of skin cancer grow very slowly and rarely spread to other parts of the body but can be locally invasive and disfiguring if left untreated.

Squamous Cell Carcinoma is a type of skin cancer that can form in both the basal and maturing suprabasal layers. SCC most commonly occur on sun-exposed areas of the body like the head, neck, arms, and back of the hands. About 2 out of 10 skin cancers are squamous cell carcinomas. Immunocompromised individuals like organ transplant recipients are more likely to have an aggressive SCC than the general population. SCC are not usually life-threatening, but account for most of the death associated with Non-melanoma skin cancers. Thus, they can be very aggressive and if left untreated can grow large and spread to other parts of the body. SCC can be found in many places on the body and can appear as a rough, scaly patch or a firm red nodule. Pre-cancerous and other skin conditions related to SCC include:  

Actinic keratosis (solar keratosis), a pre-cancerous skin condition resulting from overexposure to the sun. These pre-cancerous rough and scaly patches can range in color from brown to pink and usually start on the face, ears, backs of the hands, and arms. These patches grow slowly and do not usually cause symptoms. Actinic keratoses are considered precursors to SCC and are often treated, although their risk for conversion is low. 

Squamous cell carcinoma in situ (Bowen disease), the earliest form of squamous cell skin cancer, meaning the cancer cells are only in the epidermis and have not yet invaded to deeper layers. This skin condition appears as reddish, scaly patches and doesn’t usually cause symptoms. Bowen disease is often treated because it can progress to SCC.  

Keratoacanthoma, dome-shaped tumors found on sun-exposed skin, grow quickly and can be hard to differentiate from SCC. Doctors take a cautious approach to treating keratoacanthoma in the case the tumors turn out to be SCC. 

Melanoma is the most serious type of skin cancer that develops in the melanocytes that produce melanin, the pigment that gives the skin color. Melanoma can be found anywhere on the body. In recent years, the risk of melanoma has been increasing in people under 40, especially women. Melanomas can develop anywhere on the body and most often appear as an existing mole that has changed or a new pigmented, unusual-looking growth. 

Other less common types of skin cancer include: 

Kaposi sarcoma, a skin cancer that develops in the skin’s blood vessels and causes purple or red patches on the skin. 

Merkel cell carcinoma, causes shiny, firm nodules that occur on or just beneath the skin and around hair follicles. They arise from touch sensing cells in the skin.

Sebaceous gland carcinoma, this aggressive form of skin cancer originates in the oil glands of the skin associated with hair follicles and appears as hard, painless nodules. Most commonly found on the eyelid. 

Causes of Skin Cancer 

Skin cancer is mainly caused by the accumulation of mutations in the DNA of skin stem cells and changes in the micro-environment of the skin that promote the growth of abnormal cells. DNA contains genes that tell healthy cells what to do. Some of these genes act as tumor suppressors to block abnormal cell growth. Other genes (oncogenes) when mutated or changed promote the abnormal cell growth. Skin cancers typically inactivate tumor suppressor genes and activate oncogenes. While the accumulation of mutations is an important step in the transformation of skin cells, mutated skin cells also need a further push to become cancer. For example, excessive skin inflammation can promote the growth of abnormal skin cells. So, it may take years for abnormal skin cells to become a full-blown cancer. For these reasons, skin cancer generally is more prevalent in older individuals, although rates in younger people have been increasing in recent years. 

Most commonly, damage to DNA is caused by overexposure to ultraviolet (UV) rays from the sun or the lights used in tanning beds. Tanning is actually a response to DNA damage of epidermal cells. UV damaged cells tell melanocyte to produce and secrete melanin, making skin darker. If the damage to the skin is too great, then burning and pealing can happen. This also activates skin inflammation. On top of this, UVA rays can damage the dermis. This can induce changes in the micro-environment of the skin that can promote the growth of abnormal skin cells.   

Unfortunately, UV radiation is not the only culprit for the formation of skin cancer. Toxic chemicals in our environment can also contribute to skin cancer and tumors can develop on skin not ordinarily exposed to sunlight.

Risk Factors for Skin Cancer  

There are several factors that might increase the chance of developing liver cancer. These risk factors include:

Ultraviolet light exposure: Exposure to UVA and UVB rays is thought to be the most significant risk for developing most skin cancer types. Though UV rays make up only a small portion of the sun’s rays, they are the main cause of damage that occurs to DNA of cells and skin tissues.  

Fair skin: People with lighter skin have a much higher risk of developing skin cancer than people with naturally darker skin. Melanin has a protective effect in people with darker skin. Fair-skinned people with blue or green eyes and naturally red or blonde hair are at especially high risk of developing skin cancer. 

Age: The risk of developing non-melanoma skin cancers increases in the older population because of the buildup of sun exposure over time. These cancers, however, are becoming more common in younger people due to increased sun exposure. Excessive exposure at a young age can also increase the risk of getting skin cancer later in life.

Gender: Men are more likely than women to get basal and squamous cell cancers.

Moles: People with many moles are at an increased risk of developing skin cancer. Larger, irregular-looking moles are more likely than others to become cancerous.

Exposure to chemicals: Exposure to large amounts of arsenic increases the risk of getting skin cancer. Arsenic is naturally found in well water and is used in some pesticides.

Exposure to radiation: People who have received radiation treatment have a higher risk of developing skin cancer in the area they received the treatment.

Sunny or high-altitude climates: People who live in high-altitude, sunny climates, like Colorado, are exposed to stronger UV sunlight than people at lower elevations. The exposure to UV is greater at higher elevations.

Weakened immune system: The immune system helps fight off cancer cells. People with weakened immune systems, either from certain diseases like HIV/AIDS or from medical treatments like immunosuppressants, are more likely to develop skin cancer. 

Pre-cancerous skin lesions: Skin lesions like actinic keratoses can increase the risk of developing skin cancer.

A personal or family history of skin cancer: Those who have previously developed skin cancer or have parents or siblings with skin cancer, are at greater risk of reoccurrence.

Latest in Skin Cancer from the CU Cancer Center

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Information reviewed by Robert P. Dellavalle MD, PhD, MSPH, in October 2022.