A skin rash can occur for many reasons. It is a generic term that people use to describe any change in the skin, such as from infectious disease or an allergic reaction. On very rare occasions, a rash can be a symptom of cancer.
Knowing the difference can help a person seek the necessary help or avoid anxiety about a noncancerous rash.
Changes in the skin can occur due to a cancerous cause or a precancerous cause. In these cases, the skin symptoms are signs of an underlying condition that needs diagnosis and treatment.
In this article, we explain how to recognize potentially cancerous rashes. We also cover the different types of cancer that can cause a rash.
It is easy to confuse some noncancerous rashes for a sign of cancer.
For example, people with psoriasis will often experience persistent, scaly, red or pink plaques of skin that may sometimes itch.
The skin might also crack, which can cause further discomfort. Some people may find that this cracked skin occasionally bleeds, especially after itching.
A skin specialist, or dermatologist, can usually identify skin cancer rashes as distinct from those that are typical of psoriasis. Some people, however, may worry about skin cancer when they see a rash.
This may be because certain skin cancers frequently present with certain similar features, such as pink and red discoloration or small areas of bleeding.
It is important to remember that skin cancers are more likely to present as an isolated lesion than several lesions.
Psoriasis, on the other hand, usually presents with several lesions. Also, skin cancer lesions may not respond to typical treatments for psoriasis.
Moles that indicate melanoma look different to other moles on the body. For example, they may:
- have irregular borders
- lack symmetry
- present with a variety of colors
- be larger than 6 millimeters across
- change with time
Skin cancer rashes will typically not resolve on their own, unlike those of other skin conditions. As the cancer grows, the size and shape of the lesion or rash will usually change. It may grow into deeper layers of skin and change shape.
Skin cancer may develop in visible locations on the skin, so identifying these early on is often easier than with other types of cancer. Doing so also makes successful treatment more likely.
However, skin cancer can also develop in areas that are not easily visible, such as the back, scalp, and bottom of the feet.
Anyone who is uncertain about their skin symptoms should seek immediate consultation with a doctor or dermatologist.
Not all skin cancers will present with a rash. For example, melanomas — which develop from the melanocyte cells that provide pigment to the skin — often resemble misshapen moles.
Melanomas are one of the most life threatening forms of skin cancer, so surveillance for an early lesion is essential for prompt treatment and a good prognosis.
There are a variety of cancerous and precancerous rashes. Precancerous rashes may evolve into cancerous ones over time, and early diagnosis and treatment are vital in every case.
Below, we list the types of skin cancer that tend to cause a rash, a lesion, or other skin symptoms:
Actinic keratosis, or solar keratosis, occurs after excessive sun exposure on a particular area of the body. People with an actinic keratosis may develop a small, red, scaly patch on the skin. The patch usually does not cause symptoms.
Actinic keratosis most commonly occurs on exposed areas of the body, such as the hands, head, or neck.
These patches are precancerous lesions. Over time, there is a slight risk that they will develop into a type of cancer called squamous cell carcinoma (SCC). It can be difficult for doctors to determine whether or not an actinic keratosis patch will change over time and become cancerous.
Even though most cases of actinic keratosis do not turn into cancer, doctors still recommend early treatment and attending regular checkups to prevent the development of cancer.
Basal cell carcinomas
Basal cell carcinoma (BCC) is a type of cancer that often starts as a pearly papule or bump, often on the nose or another area of the face.
The papule may then grow and become shinier. It may start to bleed in the center, where an indentation may form.
In other areas of the body, BCC may appear as a small, scaly, pink patch or a pigmented, shiny bump. It may even present as an irregular scar.
As the cancer progresses, the area may become crusty and start to bleed or ooze.
Actinic cheilitis, also known as farmer's lip, is a precancerous rash that usually develops on the lips. The condition produces scaly patches or rough lips.
This type of rash often develops after years of exposure to ultraviolet rays. Very often, this occurs due to a large amount of time spent doing outdoor work, such as agricultural work, marine work, or jobs at a high altitude.
Without treatment, actinic cheilitis may develop into SCC.
SCC is most likely to appear as a very scaly, crusted, pink papule that bleeds easily and grows with time.
However, a rough, scaly, red patch of skin may appear instead. This can often closely resemble noncancerous or precancerous skin lesions.
Unlike skin rashes that resolve over time, rashes that occur due to SCC grow slowly and appear as a bump that does not seem to heal.
SCC typically develops on regularly exposed skin, such as the hands, arms, neck, and head. It might also develop in other regions of the body.
A cutaneous horn is a buildup of keratin cells. Keratin is the protein that makes up fingernails. These cells may group and pile up to create a growth that extends outward from the skin.
A cutaneous horn may have a red base, which, in some cases, can harbor SCC.
The growths are most common in older adults with fair skin who have a long history of sun exposure.
A rash may also be a sign of cancers that develop away from the skin, such as different forms of lymphoma.
Lymphoma is dangerous, as cancer cells circulate throughout the body. These cells may then grow in many organs or tissues at once.
In the sections below, we list some other types of cancer that may cause skin symptoms:
When lymphoma starts in the skin, it is called mycosis fungoides.
If no signs of lymphoma are present elsewhere in the body when a doctor identifies this type of cancer, they will diagnose primary cutaneous T cell lymphoma.
Mycosis fungoides is the most common type of cutaneous T cell lymphoma.
In mycosis fungoides, immune system cells in the skin become cancerous and create itchy skin changes that can mimic psoriasis or eczema.
This rash can spread and get worse over time. It may develop into tumors on the skin or travel to distant organs in the body.
Sézary syndrome occurs when T cell lymphoma turns skin bright red across a person's entire body.
A doctor will often recommend aggressive treatment methods to try to control its growth. Sézary syndrome generally has a poor outlook.
Leukemia causes a person to develop tiny red spots on their skin called petechiae, which signal that they have low platelet levels.
Broken blood vessels under the skin are the typical cause of red spots. However, they might also develop due to less severe conditions.
Children might also experience a rash due to leukemia cutis. The rash can take on a variety of appearances. Sometimes, it can cause a series of red, brown, or purple bumps on the skin.
It is important to note that excessive sun exposure does not directly cause these skin lesions.
Learn more about leukemia here.
Kaposi sarcoma can lead to deep red, purple, or brown plaques on the skin that may spread out over a section of the body, similar to a rash.
These lesions are most common on the legs and usually cause no additional symptoms.
If a person has a persistent rash of any kind, they should see a doctor — even if they think they can identify it.
Many cancers cause rashes that can resemble those of less serious skin conditions. Attending regular checkups with a dermatologist is vital for discussing any changes in the skin and avoiding complications from misdiagnosed rashes.
Sun protection is vital for helping a person prevent certain skin cancers with links to sun exposure. Effective measures include wearing:
- a sun hat
- long clothing that covers the skin on the arms and legs
The American Academy of Dermatology recommend wearing sunscreen with a sun protection factor of 30 or higher.
Taking these steps can help a person strengthen their defenses against some skin cancers.