What Are the Different Types of Skin Cancer?

Skin cancer occurs when abnormal cells in the epidermis, the outermost layer of the skin, grow at an out-of-control rate. These abnormal cells are usually caused by exposure to the sun and lead to tumors in the skin.

There are several different types of skin cancer, and they can generally be grouped into four categories: basal cell carcinoma, squamous cell carcinoma, melanoma, and Merkel cell carcinoma. 

The Skin Cancer Foundation estimates that one in five Americans will develop skin cancer by age 70. Each type has its own signs, symptoms, and risk factors.

Basal cell and squamous cell carcinomas are non-melanoma cancers and tend to be less aggressive than melanoma cancers. Melanoma and Merkel cell carcinoma are less common and more serious forms of skin cancer.

Most forms of skin cancer are very treatable, especially when caught early. 

Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common type of skin cancer and the most common of all cancers in the United States with about 4 million diagnoses each year. 

It is caused by the growth of abnormal basal cells in the epidermis. Basal cells are one of three types of skin cells, and when they are damaged by the sun or tanning bed rays, they can grow too quickly.

Signs of Basal Cell Carcinoma

Basal cell carcinoma most commonly looks like a small open sore. It could be red or pink in fair-skinned people and brown in people of color. It may present as a red patch or bump on the skin. BCC often has a raised or rolled border around the sore and may bleed or crust over. It can present differently in each individual. 

BCC is usually found on areas of the body exposed to the sun like the face, ears, neck, scalp, and shoulders. If you have experienced an open sore that doesn't heal or a red patch of skin that won’t go away, it’s best to get it checked out. BCC can also look like a shiny, pearl-like growth or a waxy scar with undefined borders. The area may itch, be painful, or have no symptoms at all. 

Who Is at Risk?

The major cause of BCC is exposure to UV rays from the sun and tanning beds. You may be at higher risk of being diagnosed with BCC if you:

• Have a history of other types of skin cancer
• Have a history of sun tanning
• Are over age 50
• Are fair-skinned
• Are male
• Have a history of chronic skin infections

Treatment

Basal cell carcinoma grows slowly, so it is very treatable. When caught early, the treatments are effective and usually leave minimal scarring, if any. The growth can be removed via surgery, radiation and/or medications. Most are outpatient procedures and require only local numbing.

Surgical options include electrosurgery, Mohs surgery, cryosurgery, laser surgery, and excisional surgery with a scalpel. Radiation may be effective at destroying the tumor without the need for cutting or medication. Topical chemotherapy creams can be applied directly to the growth and have cure rates of 80% to 90% when used early. 

The longer a skin tumor grows, the more difficult it is to treat. If left untreated, BCC can grow into other tissues and cause damage to the skin, muscles, and bones. The longer the BCC grows, the higher the chance of recurrence once it is treated. Advanced BCC may require oral chemotherapy drugs, as well as surgery and radiation. 

If you have a history of BCC, your healthcare provider will talk with you about doing skin self-exams, especially in areas frequently exposed to the sun. You can prevent BCC by taking sun protection seriously with limited exposure, frequent sunscreen applications, and wearing a wide-brimmed hat, light clothing to cover your skin and sunglasses. 

Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is the second most common type of skin cancer after basal cell carcinoma, and is caused by out-of-control growth of the squamous cells in the epidermis. Squamous cells are flat-shaped cells near the skin’s surface. About 1 million Americans are diagnosed with SCC each year. 

Signs of Squamous Cell Carcinoma

Like BCC, SCC is most commonly found in areas with frequent sun exposure like the face, ears, neck, scalp, and hands. The growths can also occur in scars or sores and look like open sores, red patches, warts or thickened skin. They can also appear in areas not affected by the sun, such as the genitals. 

The skin around an SCC growth may show signs of sun damage like wrinkling and darker pigment. They can bleed or itch as well. 

Who Is at Risk?

Much like with BCC, the more time you spend in the sun, the more at risk you are for developing SCC. About 90% of nonmelanoma skin cancers are caused by sun exposure, and people who have tanned indoors have a 67% higher risk of developing squamous cell carcinoma.

Your risk for SCC is higher if you:

• Have a history of skin cancer
• Have a history of unprotected exposure to the sun or tanning beds
• Have a weakened immune system due to a chronic condition or medication
• Are over age 50
• Are male
• Have a history of chronic skin infections, precancerous skin growths or human papillomavirus (HPV)

Treatment

When caught early, squamous cell carcinoma is curable. The early treatment options for SCC are similar to those for BCC, and include surgery, radiation, and topical treatments. Small growths that are caught early can usually be removed via surgery and won’t require additional treatments. 

If left untreated, SCC can metastasize and grow into other areas of the body. The longer it grows undetected, the harder it is to treat, especially if it reaches the lymph nodes. Each year about 15,000 people die from SCC. Fortunately, about 95% of squamous cell carcinomas are caught in the early stage and are curable. To catch SCC as early as possible, perform regular skin checks and see your healthcare provider if you have a sore that won’t heal. 

Melanoma

Melanoma is considered the most serious form of skin cancer because of its high likelihood to spread. It develops in melanocytes, the skin cells that produce pigment or melanin. These cells are found in the skin’s upper layer and are responsible for its color. When our skin is damaged by the sun, it triggers melanocytes to produce more melanin. That is why skin looks tanned after a day in the sun; that sun-kissed glow is actually skin damage.

The Skin Cancer Foundation estimates that in 2021, 207,390 Americans will be diagnosed with melanoma, and 101,280 of those cases will be invasive, meaning that they have begun to spread. Melanoma is expected to cause 7,180 deaths in the United States in 2021.

There are four types of melanoma:

• Superficial spreading melanoma is the most common form of melanoma and looks like an asymmetrical, discolored patch of skin with uneven borders
• Lentigo maligna develops most often in older individuals, and looks like a slightly raised blotchy patch of blue-black skin
• Acral lentiginous melanoma is the most common type of melanoma in people of color and commonly appears as a black or brown area under the nail or on the soles of the feet
• Nodular melanoma is the most aggressive form of melanoma and usually presents as a black or blue bump on the skin; it can also be red or pink in color

Signs of Melanoma

Melanoma growths usually look like moles that are brown or black. They can sometimes grow out of a previously benign mole. It is estimated that about 20% to 30% of melanomas grow out of existing moles and 70% to 80% occur on normal-looking skin. Melanoma growths are related to sun exposure, but can also grow in areas that don’t receive much sunlight. The most common site for women is the legs and the trunk of the body for men. 

The best way to spot melanoma is by keeping an eye on any skin growths that are new or changing. When checking yourself for melanoma, remember the ABCDEs:

• Asymmetry: When a mole or growth has two halves that do not match
• Border: A border that is jagged or undefined means your mole should be evaluated
• Color: Multiple colors are a warning sign of melanoma
• Diameter: If you notice a mole or growth that is larger than the size of a pea, it needs to be seen
• Evolving: Any new or changing moles should be evaluated for melanoma

Who Is at Risk?

Like other types of skin cancer, melanoma is caused by sun damage. Ultraviolet rays from the sun or tanning bed cause damage to the DNA in your skin cells. At first your immune system can repair the damage, but over time the mutations in the DNA of the cell can cause skin cancer to develop. 

Melanoma is most often caused by intense sun exposure that leaves a significant sunburn. In fact, your risk of melanoma doubles if you have a history of five or more sunburns in your lifetime.

Your risk for melanoma is higher if you:

• Have a history of skin cancer
• Have unprotected exposure to the sun or tanning beds
• Have a history of melanoma in your family
• Have a weakened immune system due to a chronic condition or medication
• Have a high number of moles on your body
• Are fair-skinned 

Melanoma can run in families. It’s estimated that about one in 10 patients with melanoma has a family member who has already been diagnosed with the condition. If you have both a family history and a large number of moles, then you are at higher risk and have what dermatologists call familial atypical multiple mole melanoma syndrome (FAMMM). 

Treatment

While melanoma is more serious than other types of skin cancer, it is still treatable and curable when caught early. When it spreads into other tissues and areas of the body, it becomes more challenging to treat. 

Treatment options for melanoma include surgical removal, radiation, chemotherapy, immunotherapy, and targeted therapy. Early-stage melanomas that have not spread beyond the first layer of skin can usually be surgically removed, much like basal cell carcinomas and squamous cell carcinomas.

Melanomas that have spread can be treated with immunotherapy, which are medications that stimulate the immune system to destroy cancer cells. This treatment option is usually more effective and results in fewer side effects than chemotherapy. Targeted therapies can use drugs to attack melanoma cells by acting on the genes themselves. Chemotherapy and radiation may also be used. 

The five-year survival rate for Americans whose melanoma is caught early is 99%. The survival rate falls to 65% if the melanoma has already spread to the lymph nodes and 25% if it has reached other body organs.

Interestingly, the survival rate for individuals who have a family history of melanoma is higher than people without a family history. This is believed to be due to the fact that those with a family history are more diligent about skin checks and seeing their dermatologists for any concerns, which helps them spot cancer earlier. 

Merkel Cell Cancer

Merkel cell cancer is a rare, aggressive form of skin cancer. Each year about 3,000 Americans are diagnosed with Merkel cell cancer, and it's estimated to cause 700 deaths annually. It is 40 times rarer than melanoma, and is more likely to spread and return once treated. 

Merkel cells are found deep in the skin’s outermost layer. They are connected to the nerves and functions such as touch receptors, which send messages about touch and sensation to the brain. 

Signs of Merkel Cell Cancer

Merkel cell cancer growths usually appear as firm, painless bumps or sores. They are found on sun-exposed areas of the body, especially the head, neck, and eyelids. The growths look like pearly pimple-like lumps and may be difficult to recognize. They can be pink, red, or purplish-blue. They usually grow quickly, which is why they are three to five times deadlier than melanoma. 

A helpful way to spot Merkel cell cancer is by using the AEIOU tool:

• Asymptomatic: Most lesions are not painful or tender to the touch
• Expanding: Merkel cell cancer growths expand and grow quickly
• Immunocompromised: A compromised immune system puts someone at higher risk
• Older: More common in individuals over age 50
• UV-exposed skin: Lesions are more likely to present on sun-exposed skin (but not always)

Who Is at Risk?

Merkel cell cancer can grow in areas of the body that do not receive sunlight, as well as those that frequently get sun exposure. Unlike other forms of skin cancer, Merkel cell cancer is associated with a virus called the Merkel cell polyomavirus. It’s unclear how much having the virus raises someone's risk of Merkel cell cancer because the virus is very common while Merkel cell cancer is quite rare. 

Your risk for Merkel cell cancer increases if you:

• Have a history of skin cancer 
• Have unprotected exposure to the sun
• Have a weakened immune system
• Are fair-skinned
• Are over age 50
• Are male 

Treatment

Merkel cell cancer is dangerous but treatable when caught early. Because it is so rare, the Skin Cancer Foundation recommends finding a healthcare provider or academic medical center with specialized expertise in this type of cancer. Treatment will depend on how advanced the cancer is, but usually includes a combination of radiation, immunotherapy, and chemotherapy.

Rarer Types of Skin Cancer

Basal cell carcinoma, squamous cell carcinoma, melanoma, and Merkel cell cancer make up the vast majority of all skin cancer cases. However, there are several other rare types of skin cancer:

• Cutaneous T-cell lymphoma can affect the skin, blood, lymph nodes, and internal organs. It presents as a dry, itchy red rash.
• Dermatofibrosarcoma protuberans (DFSP) causes a tumor in the deep layers of the skin and starts out as a patch of firm skin that raises over time. The tumors have a high rate of recurring or returning once treated. 
• Kaposi's sarcoma is a rare cancer caused by an infection with human herpesvirus-8 (HHV-8). It causes abnormal tissue growth under the skin, and looks like red and purple lesions. Those with a compromised immune system, such as people who are HIV-positive, are more at risk.
• Sebaceous carcinoma is a rare, aggressive cancer that usually affects the skin on or around the eyelid. It presents as a small, round, painless tumor on the upper or lower eyelid.
• Skin adnexal tumors are very rare tumors that grow in the sebaceous glands or hair follicles. They are often misdiagnosed as benign growth, and almost always require a pathologist to diagnose. 
• Soft tissue sarcomas are cancerous growths that can develop in the deep layers of skin, as well as the body’s fat, muscle, nerves and blood vessels. 

Precancerous Skin Conditions

Some precancerous growths, often attributable to sun exposure, can lead to skin cancer over time. However, if they are recognized and removed early, you could avoid a cancer diagnosis. These growths include:

• Actinic keratosis: About 40% to 60% of squamous cell cancer cases began as actinic keratosis. Anywhere between 2% to 10% of these growths will develop into SCC, sometimes in as little as a couple of years. Actinic cheilitis is a type of actinic keratosis that appears on the lower lip, and is at higher risk for developing into skin cancer.
• Bowen’s disease: This early, noninvasive form of SCC is at high risk of becoming skin cancer if not addressed. It presents as an eczema-like scaly patch and is usually red or brown in color. These growths have been linked to sun exposure, radiation, carcinogen exposure, genetics, and trauma. 
• Leukoplakia: These white patches on the lips, tongue, and gums may be caused by alcohol and tobacco use, and can turn into squamous cell carcinoma. Cancer sites on the lips may be caused by sun damage.
• Keratoacanthoma: This dome-shaped growth is usually found on sun-exposed skin and usually grows quickly at first, then slows down. Many shrink and go away on their own, but if they continue to grow, this tumor can turn into squamous cell carcinoma. They are usually removed surgically.