Skin cancer is the uncontrolled growth of abnormal skin cells. It occurs when unrepaired DNA damage to skin cells (most often caused by ultraviolet radiation from sunshine or tanning beds) triggers mutations, or genetic defects, that lead the skin cells to multiply rapidly and form malignant tumors.


Melanoma occurs when something goes awry in the melanin-producing cells (melanocytes) that give color to your skin.

Usually, skin cells develop in a controlled and orderly way — healthy new cells push older cells toward your skin's surface, where they die and eventually fall off. But when some cells develop DNA damage, new cells may begin to grow out of control and can eventually form a mass of cancerous cells.


Skin cancer begins in the cells that make up the outer layer (epidermis) of your skin. One type of skin cancer called basal cell carcinoma starts in the basal cells, which make skin cells that continuously push older cells toward the surface. As new cells move upward, they become flattened squamous cells, where a skin cancer called squamous cell carcinoma can occur. Melanoma, another type of skin cancer, arises in the pigment cells (melanocytes).

Just what damages DNA in skin cells and how this leads to melanoma isn't clear. It's likely that a combination of factors, including environmental and genetic factors, causes melanoma. Still, doctors believe exposure to ultraviolet (UV) radiation from the sun and tanning lamps and beds is the leading cause of melanoma.

The UV light doesn't cause all melanomas, especially those that occur in places on your body that don't receive exposure to sunlight. This indicates that other factors may contribute to your risk of melanoma.
















The most dangerous form of skin cancer, these cancerous growths develop when unrepaired DNA damage to skin cells (most often caused by ultraviolet radiation from sunshine or tanning beds) triggers mutations (genetic defects) that lead the skin cells to multiply rapidly and form malignant tumors. These tumors originate in the pigment-producing melanocytes in the basal layer of the epidermis. Melanomas often resemble moles; some develop from moles. The majority of melanomas are black or brown, but they can also be skin-colored, pink, red, purple, blue or white. Melanoma is caused mainly by intense, occasional UV exposure (frequently leading to sunburn), especially in those who are genetically predisposed to the disease.

An estimated 192,310 cases of melanoma will be diagnosed in the U.S. in 2019. Of those, 95,830 cases will be in situ (noninvasive), confined to the epidermis (the top layer of skin), and 69,480 cases will be invasive, penetrating the epidermis into the skin’s second layer (the dermis).

If melanoma is recognized and treated early, it is almost always curable, but if it is not, cancer can advance and spread to other parts of the body, where it becomes hard to treat and can be fatal. While it is not the most common of skin cancers, it causes the most deaths. An estimated 7,230 people will die of melanoma in 2019. Of those, 4,740 will be men and 2,490 will be women.


Melanoma is a form of skin cancer that begins in the cells (melanocytes) that control the pigment in your skin. This illustration shows melanoma cells extending from the surface of the skin into the deeper skin layers.

Warning signs

Moles, brown spots and growths on the skin are usually harmless — but not always. Anyone who has more than 100 moles is at higher risk for melanoma. The first signs can appear in one or more atypical moles. That's why it's so important to get to know your skin very well and to recognize any changes in the moles on your body. Look for the ABCDE signs of melanoma, and if you see one or more, make an appointment with a physician immediately.

Actinic Keratosis (AK)

A potential precancer. An actinic keratosis (AK), also known as solar keratosis, is a crusty, scaly growth caused by damage from exposure to ultraviolet (UV) radiation. You’ll often see the plural, “keratoses,” because there is seldom just one. AK is considered a precancer because if left alone, it could develop into skin cancer, most often the second most common form of the disease, squamous cell carcinoma (SCC). More than 419,000 cases of skin cancer in the U.S. each year are linked to indoor tanning, including about 168,000 squamous cell carcinomas.

The most common type of precancerous skin lesion, AKs appear on skin that has been frequently exposed to the sun or artificial sources of UV light, such as tanning machines. In rare instances, extensive exposure to X-rays can cause them. Above all, they appear on sun-exposed areas such as the face, bald scalp, ears, shoulders, neck and the back of the hands and forearms. They can also appear on the shins and other parts of the legs. They are often elevated, rough in texture and resemble warts. Most become red, but some are light or dark tan, white, pink and/or flesh-toned. They can also be a combination of these colors.

In the beginning, AKs are frequently so small that they are recognized by touch rather than sight. They feel as if you were running a finger over sandpaper. Patients may have many times more invisible (subclinical) lesions than those appearing on the surface.

Most often, actinic keratoses develop slowly and reach a size from an eighth to a quarter of an inch. Early on, they may disappear only to reappear later. Occasionally they itch or produce a pricking or tender sensation. They can also become inflamed and surrounded by redness. In rare instances, AKs can even bleed.



Atyptical Moles are unusual-looking benign (noncancerous) moles, also known as dysplastic nevi (the plural of “nevus,” or mole). Atypical moles may resemble melanoma, and people who have them are at increased risk of developing melanoma in a mole or elsewhere on the body. The higher the number of these moles someone has, the higher the risk. Those who have 10 or more have 12 times the risk of developing melanoma compared with the general population.

Heredity appears to play a part in the formation of atypical moles. They tend to run in families, especially in Caucasians; about 2 to 8 percent of Caucasians have these moles. Those who have atypical moles plus a family history of melanoma (two or more close blood relatives with the disease) have a very high risk of developing melanoma. People who have atypical moles, but no family history of melanoma, are also at higher risk of developing melanoma compared with the general population. So are those with 50 or more normal moles. All of these high-risk individuals should practice rigorous daily sun protection, perform a monthly skin self-examination head to toe and seek regular professional skin exams.

Some people have so many regular and atypical moles that they are classified as having atypical mole syndrome. People with “classic” atypical mole syndrome have the following three characteristics:

  • 100 or more moles

  • One or more moles 1/3 inch (8 mm) or larger in diameter

  • One or more moles that are atypical.

At even higher risk of developing melanoma are those with familial atypical multiple mole melanoma syndromes (FAMMM). These people have not only atypical mole syndrome but also one or more first- or second-degree relatives with melanoma. While atypical moles often arise in childhood, they can appear at any time of life in people with FAMMM.


The most frequently occurring form of skin cancer. BCCs are abnormal, uncontrolled growths or lesions that arise in the skin’s basal cells, which line the deepest layer of the epidermis (the outermost layer of the skin). BCCs often look like open sores, red patches, pink growths, shiny bumps, or scars and are usually caused by a combination of cumulative and intense, occasional sun exposure.

BCC almost never spreads (metastasizes) beyond the original tumor site. Only in exceedingly rare cases can it spread to other parts of the body and become life-threatening. It shouldn’t be taken lightly, though: it can be disfiguring if not treated promptly.

More than 4 million cases of basal cell carcinoma are diagnosed in the U.S. each year. In fact, BCC is the most frequently occurring form of all cancers. More than one out of every three new cancers is a skin cancer, and the vast majority are BCCs.


Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer that is at high risk of recurring and spreading (metastasizing) throughout the body, with most recurrences taking place within two years after diagnosis of the primary tumor. While the disease is 40 times rarer than melanoma (an estimated 0.24 cases per 100,000 persons in the U.S, or about 2,500 cases total),  it kills about one in three patients compared with one in nine for melanoma. Approximately 700 people die from MCC each year in the U.S. 

MCC most often arises on sun-exposed areas in fair-skinned individuals over age 50. Its name comes from the similarity of these cancer cells to normal Merkel cells in the skin that are thought to be associated with touch sensation. Normal Merkel cells were first described more than 100 years ago by Friedrich Sigmund Merkel. 


Normal Merkel cells in the skin: In this illustration of a cross-section of skin, normal Merkel cells are shown in red and connect to nerves shown in yellow. The structures drawn include the epidermis (upper third), dermis (middle), and deeper adipose layer containing the fatty tissue. Arteries are depicted as red and veins are blue.



Squamous cell carcinoma (SCC), the second most common form of skin cancer, is an uncontrolled growth of abnormal cells arising from the squamous cells in the epidermis, the skin’s outermost layer. It is sometimes called cutaneous squamous cell carcinoma (CSCC) to differentiate it from very different kinds of SCCs elsewhere in the body. Cutaneous is the scientific word for “related to or affecting the skin.”

SCCs often look like scaly red patches, open sores, warts or elevated growths with a central depression; they may crust or bleed. They can become disfiguring and sometimes deadly if allowed to grow. More than 1 million cases of squamous cell carcinoma are diagnosed each year in the U.S., which translates to about 115 cases diagnosed every hour. Incidence has increased up to 200 percent in the past three decades in the U.S., and more than 15,000 Americans die each year from the disease.

Cumulative, long-term exposure to ultraviolet (UV) radiation from the sun over your lifetime causes most SCCs. Daily year-round sun exposure, intense exposure in the summer months or on sunny vacations and the UV produced by indoor tanning devices all add to the damage that can lead to SCC. Experts believe that indoor tanning is contributing to an increase in cases among young women, who tend to use tanning beds more than others do.

SCCs may occur on all areas of the body, including the mucous membranes and genitals, but are most common in areas frequently exposed to the sun, such as the rim of the ear, lower lip, face, balding scalp, neck, hands, arms, and legs. The skin in these areas often reveals telltale signs of sun damage, including wrinkles, pigment changes, freckles, “age spots,” loss of elasticity and broken blood vessels.

What you should know about melanoma

Melanoma is not the most common type of skin cancer, but it is the most serious because it often spreads. Risk factors for melanoma include overexposure to the sun.

This article explains the symptoms of melanoma, how it is diagnosed, and how it is treated. We also explain how best to prevent melanoma.


  • The incidence of melanoma appears to be increasing for people under the age of 40 years, especially women.

  • Avoiding sunburn is an effective way to reduce the risk of skin cancer.

  • Self-monitoring of moles and other markings on the skin can help with early detection.

Melanoma is a form of skin cancer that arises when pigment-producing cells—known as melanocytes—mutate and become cancerous.

Most pigment cells are found in the skin, but melanoma can also occur in the eyes (ocular melanoma) and other parts of the body, including, rarely, the intestines. It is rare in people with darker skin.

Melanoma is just one type of skin cancer. It is less common than basal cell and squamous cell skin cancers, but it can be dangerous because it is more likely to spread, or metastasize.

Melanomas can develop anywhere on the skin, but certain areas are more prone than others. In men, it is most likely to affect the chest and the back. In women, the legs are the most common site. Other common sites are the neck and face.

According to the National Cancer Institute, about 87,110 new melanomas were expected to be diagnosed in 2018, and about 9,730 people were expected to die of melanoma.


The stage at which cancer is diagnosed will indicate how far it has already spread and what kind of treatment is suitable.

One method of staging melanoma describes cancer in five stages, from 0 to 4.

Stage 0: The cancer is only in the outermost layer of skin and is known as melanoma in situ.

Stage 1: The cancer is up to 2 millimeters (mm) thick. It has not spread to lymph nodes or other sites, and it may or may not be ulcerated.

Stage 2: The cancer is at least 1.01 mm thick and it may be thicker than 4 mm. It may or may not be ulcerated, and it has not yet spread to lymph nodes or other sites.

Stage 3: Cancer has spread to one or more lymph nodes or nearby lymphatic channels, but not to distant sites. Original cancer may no longer be visible. If it is visible, it may be thicker than 4 mm, and it may also be ulcerated.

Stage 4: Cancer has spread to distant lymph nodes or organs, such as the brain, lungs, or liver.


There are four main types of skin melanoma:

Superficial spreading melanoma is the most common type. It is more commonly found on the arms, legs, chest, and back. The melanoma cells usually grow slowly at first and spread out across the surface of the skin.

Nodular melanoma is the second most common type. It can grow more quickly than other melanomas. It is also more likely to lose its color when growing, becoming red rather than black. It is more commonly found on the chest, back, head or neck.

Lentigo maligna melanoma is less common. It is usually found in older people, in areas of skin that have had a lot of sun exposure over many years. It is often found on the face and neck. It develops from a slow-growing precancerous condition called a lentigo maligna or Hutchinson’s freckle. This looks like a stain on the skin. They are usually slow-growing and less dangerous than the other types of melanoma.

Acral lentiginous melanoma is the rarest type. It is usually found on the palms of the hands, soles of the feet, or under fingernails or toenails. It is more common in people with black or brown skin. It is not thought to be related to sun exposure.

Another rare type of melanoma is desmoplastic melanoma.

Rarely, melanoma can start in parts of the body other than the skin. It can start in the eye (ocular melanoma). Or it can start in the tissues that line areas inside the body, such as the anus or rectum (anorectal melanoma), nose, mouth, lungs and other areas.


As with all cancers, research is ongoing into the causes of melanoma.

People with certain types of skin are more prone to developing melanoma, and the following factors are associated with an increased incidence of skin cancer:

  • High freckle density or tendency to develop freckles after sun exposure

  • The high number of moles

  • Five or more atypical moles

  • Presence of actinic lentigines, small gray-brown spots, also known as liver spots, sun spots, or age spots

  • Giant congenital melanocytic nevus, brown skin marks that present at birth, also called birthmarks

  • Pale skin that does not tan easily and burns, plus light-colored eyes

  • Red or light-colored hair

  • High sun exposure, mainly if it produces blistering sunburn, and especially if sun exposure is intermittent rather than regular

  • Age, as risk increases with age

  • Family or personal history of melanoma

  • Having an organ transplant

Of these, only high sun exposure and sunburn are avoidable.

The World Health Organization (WHO) estimates that around 60,000 early deaths occur each year worldwide because of excessive exposure to the sun's ultraviolet (UV) radiation. An estimated 48,000 of these deaths are from malignant melanoma.

Avoiding overexposure to the sun and preventing sunburn can significantly lower the risk of skin cancer. Tanning beds are also a source of damaging UV rays.



As with other forms of cancer, the early stages of melanoma may be hard to detect, so it is essential to check the skin actively for signs of change.

Alterations in the appearance of the skin are vital indicators of melanoma and are used in the diagnostic process.

The Melanoma Research Foundation has produced a web page that compares pictures of melanoma with those of normal moles.

This American non-profit organization also lists the symptoms and signs that should prompt a visit to the doctor.

These are:

skin changes, such as a new spot or mole or a change in color, shape, or size of a current spot or mole

  • A skin sore that fails to heal

  • A spot or sore that becomes painful, itchy, or tender, or which bleeds

  • A spot or lump that looks shiny, waxy, smooth, or pale.

  • A firm red lump that bleeds or appears ulcerated or crusty

  • A flat, red spot that is rough, dry, or scaly


The ABCDE examination of skin moles is also an essential way to reveal suspect lesions. It describes five simple characteristics to look out for in melanoma appearance:

Asymmetric: normal moles are often round and symmetrical, whereas one side of a cancerous mole is likely to look different from the other side - not round or symmetrical.

Border: this is likely to be irregular rather than smooth - ragged, notched, or blurred.

Color: melanomas tend not to be of one color but to contain uneven shades and colors, including varying black, brown, and tan, and even white or blue pigmentation.

Diameter: a change in the size of the mole, or a mole that is larger than an ordinary mole (more than a quarter inch in diameter) can indicate skin cancer.

Evolving: a change in a mole's appearance over a period of weeks or months can be a sign of skin cancer.


The treatment of skin cancer is similar to that of other cancers, but, unlike many internal cancers, it is easier to access cancer to remove it completely. Surgery is the most common treatment for melanoma.

Surgery involves removing the lesion and some of the healthy tissue around it. A biopsy may be taken at the same time.

If melanoma covers a large area of skin, a skin graft may be necessary. If cancer may have penetrated the lymph nodes, a lymph node biopsy may be performed.

Other, less common treatments for skin cancer include:

  • Chemotherapy

  • Biological therapy, using drugs that work with the immune system

Rarely, photodynamic therapy, which uses a combination of light and drugs, and radiation are used.


Most cases of melanoma affect the skin. They usually produce changes in existing moles. A person to detect the early signs of melanoma themselves by regularly examining moles and other colored blemishes and freckles.

Any changes in the appearance of the skin should prompt further examination by a doctor. The back should also be checked regularly, especially as 1 in 3 melanomas in men occurs on the back. A partner, family member, friend, or doctor can help check the back and other hard-to-see areas.

Cancer doctors are most concerned with lesions that "stand out from the crowd." The ABCDE checklist described above can help with this.

Eye Cancer 

(Ocular Melanoma)

Eye cancer is rare. Several different cancers can affect the eye. Eye (ocular) melanoma is the most common.

Eye melanoma usually doesn’t cause any symptoms and may be found by an optician during a routine eye test. Signs and symptoms can include:

  • Blurred vision

  • Seeing flashing lights and shadows

  • Brown or dark patches on the white area of the eye.

Other eye conditions can cause these symptoms but it’s a good idea to get them checked.

If you are diagnosed with eye melanoma, you will have further tests to find out the stage and grade of cancer. This helps doctors plan the best treatment for you. Treatment aims to destroy the cancer cells while doing as little damage to your eyesight as possible.

It’s natural to be feeling lots of different emotions at this difficult time. You may find it helps to talk about your worries with someone.


Risk factors and causes of eye melanoma

The cause of eye melanoma is not known. The main risk factor for skin melanoma is exposure to ultraviolet (UV) rays, either from the sun, sunbeds or sunlamps.

Eye melanoma is more common in people with fair or red hair, blue eyes and whose skin burns easily. But it's still not clear whether there is a link between UV ray exposure and eye melanoma.

Eye melanoma is more common in people who have atypical mole syndrome, which is also called dysplastic naevus syndrome. People with this condition often have more than 100 moles on their body and are more likely to develop a skin melanoma.

Conjunctival melanoma usually develops from a rare condition called primary acquired melanosis (PAM), which causes brown or dark patches (pigmentation) on the conjunctiva. Sometimes the melanoma will develop from an existing freckle or mole on the conjunctiva.

Signs and symptoms of eye melanoma

Eye melanoma doesn’t usually cause any symptoms. An optician may find it during a routine eye test. However, signs and symptoms can include:

  • Blurred vision

  • Seeing flashing lights and shadows

  • Brown or dark patches on the white area of the eye.

These symptoms are common to other conditions of the eye, but tell your GP or optician if you notice them.

How eye melanoma is diagnosed

You usually start by seeing your optician or GP. If they are unsure what the problem is, they will refer you to a hospital eye specialist doctor (ophthalmologist).

At the hospital, the specialist doctor will examine you. They may use the following tests to diagnose eye melanoma.

Eye drops

The doctor may put eye drops in your eye before or during some of these tests. This opens up (dilates) your pupil and makes it easier to examine your eyes. The drops will make your eyesight blurry for several hours, and you might find bright lights uncomfortable.

Don’t drive until your eyesight returns to normal.

Examining your eye

The doctor looks at the inside of your eye using a small, handheld lens and light (ophthalmoscope). Or they may use a larger microscope that sits on a table (slit-lamp biomicroscope), which you look into. They may put eye drops in your eye to open up your pupil.

Ultrasound scan

This scan uses sound waves to build up a picture on a computer screen of the inside of your eye and nearby areas. The doctor gently presses a small probe against your closed eyelid and moves it over the skin. This is painless and usually only takes a few minutes.

Fluorescein angiography

The doctor uses this test to examine the back of your eye. They put eye drops in your eye to open up your pupil, and they inject a dye, called fluorescein, into a vein in your arm. The doctor uses a special camera to take photos of the dye as it moves through the blood vessels at the back of your eye.

You may feel warm or flushed for a short time after the injection. After the test, your urine will be bright yellow, and your skin may be slightly yellow. The dye causes this. It’s harmless and only lasts a few days.


Doctors can often diagnose eye melanoma by examining the eye with the tests we mention above. But some people may need to have a small piece of tissue or cells (biopsy) removed from the eye using a fine needle. You are more likely to have a biopsy if your specialist thinks you may have a conjunctival melanoma.

A biopsy is only done by expert eye doctors who can do it quickly and without causing you pain. You can have it done using a local anesthetic, or sometimes with a general anesthetic.

Afterward, a pathologist (a doctor who specializes in analyzing cells) examines the tissue under a microscope to look for cancer cells or conditions that may develop into melanoma if left untreated.