The first sign of skin cancer is usually a change in the skin, such as an emerging lump, a new mole, or alterations to an existing mole. Identifying any changes early can facilitate a prompt diagnosis of cancer, which may improve a person’s outlook.

There are many types of skin cancer, but they fall into two distinct categories: melanoma and non-melanoma. Melanoma is less common than non-melanoma but more dangerous.

This article looks at several types of melanoma and non-melanoma skin cancers, what causes them, and how they appear on the skin. It also discusses how to reduce the risk of developing skin cancer.

There are many types of non-melanoma skin cancer, but the two most common types are basal cell carcinoma and squamous cell carcinoma.

Basal cell carcinoma

Basal cells are those at the base of the epidermis, which is the outermost layer of the skin.

According to the American Cancer Society (ACS), basal cell carcinoma is the most common form of skin cancer in the United States. It accounts for about 80% of all skin cancers.

The risk of basal skin carcinoma increases with age, with a median age of diagnosis of 68 years. However, it can also occur in younger people, especially those who have had a significant amount of sun exposure.

The appearance of basal cell carcinoma can vary, but it may present as:

  • an open sore that remains open for weeks
  • a sore that oozes, weeps, crusts over, or bleeds
  • a shiny, pearly bump
  • a sore with a sunken center

Squamous cell carcinoma

This type of carcinoma forms in the cells at the top of the epidermis.

A 2025 study highlights that there were 2,275,834 cases of squamous cell skin carcinoma worldwide in 2021. North America had the highest prevalence, with around 1,830,711 cases.

The study authors predict that the prevalence of squamous cell skin cancer will continue to increase with time.

Squamous cell carcinoma can look like:

  • a persistent open sore
  • a scaly, crusted patch that may bleed and will not resolve
  • a crusty, wart-like growth

Merkel cell carcinoma

This rare and aggressive form of cancer is becoming more common and accounts for around 3,000 cancer diagnoses in the United States each year.

Merkel cell carcinoma can present as:

  • a firm, shiny, painless lump
  • a round, raised lesion
  • a fast-growing bump

Although melanoma skin cancers are less common than non-melanoma ones, they are more likely to spread and grow.

There are four main types of melanoma skin cancers:

  • superficial spreading melanoma
  • nodular melanoma
  • lentigo maligna melanoma
  • acral lentiginous melanoma.

Superficial spreading melanoma

This is the most common form of melanoma, accounting for around 70% of cases. It can appear within an existing mole or present as a new lesion on a person’s skin.

Superficial spreading melanoma may appear as:

  • a flat patch of discolored skin
  • a lesion with an irregular shape
  • a growth that changes in size, shape, or color
  • a patch with undefined borders

Nodular melanoma

This is an aggressive form of melanoma. It grows vertically down into the skin, which makes it particularly dangerous. As it grows rapidly, it is usually more advanced at the point of diagnosis.

It accounts for around 20% of all melanomas.

Nodular melanoma can look like:

  • a raised, round lump
  • a bump that is painful and may bleed
  • a mushroom-like growth with a smooth or rough surface
  • a lump that is more than 6 millimeters (mm) across

Lentigo maligna melanoma

This type of melanoma has close links with sun exposure. It is more common in older adults and individuals who have had a lot of sun exposure, including those who work outdoors.

It usually appears on sun-damaged areas of skin, such as the face, ears, arms, and torso.

  • flat patches of skin that resemble a large dark freckle
  • patches that change shape and grow
  • a patch that is irregular in color
  • a lesion that can be painful and bleed

Acral lentiginous melanoma

This is the most common form of melanoma in people with darker skin tones. It usually appears on the soles of the feet, the palms of the hands, nail beds, and other hard-to-detect areas.

It can look like:

  • a patch that is darker than the surrounding skin
  • a lesion with an irregular, bumpy, warty surface
  • a lesion that bleeds

Most skin cancers develop due to repeated, unprotected exposure to UV radiation. Although this is usually from the sun, it can also come from other sources of UV radiation, such as tanning beds.

Having a family history of skin cancer can make a person more likely to develop it themself.

Similarly, certain gene changes can increase a person’s risk of getting skin cancer. Changes in tumor-suppressing genes, including TP53 and PTCH1, can make an individual more susceptible to cancer.

There is also an association between squamous cell carcinoma and some types of human papillomavirus (HPV). Some HPV types may interfere with typical controls on skin cell growth, potentially contributing to the development of skin cancer.

Other factors that may increase the risk of certain types of skin cancer include:

A change in the skin can indicate skin cancer. This can be a new growth, an open sore that does not heal, or a change in an existing mole.

The ACS recommends using the ABCDE rule to identify a potential melanoma:

  • A — Asymmetrical: Does it have an irregular shape?
  • B — Border: Does it have an irregular or jagged border?
  • C — Color: Is its color uneven?
  • D — Diameter: Is it larger than a pea (about 6 mm)?
  • E — Evolving: Has it changed in any way over the last few weeks or months?

Although there is no way to fully eliminate the risk of cancer, following sun safety guidance will likely reduce a person’s risk. People can help protect themselves by:

  • avoiding prolonged exposure when UV rays are at their strongest, which is typically between 10 a.m. and 4 p.m.
  • staying in the shade where possible
  • wearing protective clothing, such as a wide-brimmed hat and clothes that cover the arms and legs
  • wearing wraparound sunglasses that block UVA and UVB rays
  • using a broad-spectrum sunscreen with an SPF of at least 30
  • avoiding tanning booths and sunlamps

It is also helpful to check the skin regularly for any changes that could indicate early stage skin cancer. People can see a dermatologist about skin changes or to have a professional skin exam.

UV light can damage the DNA in skin cells. If this DNA damage affects genes that control how skin cells grow and divide, the cells may begin to grow uncontrollably and eventually form cancerous growths.

Skin cancer is the most common form of cancer in the United States. The Skin Cancer Foundation states that 1 in 5 people in the U.S. will develop skin cancer before the age of 70 years.

Although melanoma is less common than other skin cancers, it is more dangerous because it can easily spread to other parts of the body. As a result, timely identification and treatment are essential.

Yes, it can. However, it depends on the type of skin cancer and its stage.

Non-melanoma skin cancers are less likely to spread. Basal cell carcinoma usually does not spread to other parts of the body, but there is a small chance that squamous cell cancer will.

Melanoma skin cancer spreads more readily than non-melanoma, making it more dangerous. It can spread to the lymph nodes and, from there, to other organs in the body.

Up to 1 in 5 people in the U.S. will develop skin cancer at some point in their life.

Doctors generally classify the different types as either non-melanoma or melanoma cancer. Non-melanoma is usually less dangerous and less likely to spread, whereas melanoma is more aggressive.

Knowing the signs of skin cancer can help people identify a potential lesion early and seek treatment. People who wish to reduce their risk of skin cancer should practice sun safety and avoid indoor tanning.