Precancerous Skin

What Is It, Appearance, Causes, Diagnosis, Treatment, and More

Author: Armata Nikol Natalia

Editors: Lisa Miklush, PhD, RN, CNS, Ahaana Singh

Illustrator: Jillian Dunbar


What is precancerous skin?

Precancerous skin consists of various premalignant changes in the skin cells that increase the likelihood of developing into skin cancer. These changes often appear as growths or lesions. Precancerous lesions can be found on the outermost layer of skin (epidermis). They are usually seen in sun-exposed areas of the body—such as the head, hands, and forearms—and are mostly found in older adults. Precancerous skin can be considered a cancer warning sign, as it may naturally progress into squamous or basal cell carcinoma, which are two types of skin cancer that differ in prevalence and prognosis. 

The main types of precancerous lesions include actinic keratosis, actinic cheilitis, Bowen disease, and leukoplakia. Commonly known as squamous cell carcinoma in situ (SCCIS),  Bowen disease often progresses to squamous cell carcinoma (SCC), which is a type of skin cancer characterized by the accelerated growth of flat squamous cells located near the skin’s surface. Actinic keratosis and actinic cheilitis represent early lesions that may also progress to SCC. On the other hand, leukoplakia is usually a benign condition; in some cases, however, it may progress to SCC affecting the mouth.

What does precancerous skin cancer look like?

Precancerous skin growths can have a variety of colors, shapes, and textures depending on the types of lesion. Some have a characteristic appearance, while others are more easily identified when touched. However, not all cases are easily detectable and must be properly assessed for early detection of precancerous skin.

Actinic keratosis (AK), for example, usually appears as small, scaly, or crusty patches that can be pink, red, or varying colors throughout the lesion. Because of their rough and often bumpy texture, AK is easier to feel than to see. Actinic cheilitis is a variant of AK and presents with similar dry, flaky patches mainly affecting the lower lip. This can sometimes lead to small visible wrinkles or ulcers on the lip. Bowen disease also presents with red and scaly, dry patches, however, these patches tend to be larger than those associated with AK. Finally, leukoplakia refers to a white lesion, usually inside the mouth, that has an irregular shape and raised borders.

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What causes precancerous skin?

The most common cause of precancerous skin is damage to the DNA inside skin cells. Damage to DNA can cause changes in various genes that usually control cell growth, prolong cell survival, manage cell division, and prevent unwanted cell death. If such changes occur, they can progressively result in uncontrolled cell growth, known as cancer.

What are the risk factors for precancerous skin?

A wide variety of genetic and environmental risk factors can lead to DNA damage and consequent development of precancerous skin. These can include certain personal characteristics, exposure to UV radiation, certain viral infections, and some genetic conditions.

Personal characteristics and history

Individuals with lighter pigmentation of their skin, natural hair color, and eye color are more sensitive to developing precancerous skin growths. Similarly, sensitive skin types, such as those prone to developing sunburns, freckles, or moles when exposed to the sun, are also at a higher risk. Additionally, smoking is the most common risk factor for the development of leukoplakia in and around the mouth. Individual and family history of various types of skin cancer can also increase the likelihood of developing precancerous skin. Although it can affect anyone, precancerous skin occurs most commonly in older adults. 

UV rays

Ultraviolet (UV) radiation, which occurs naturally from the sun or artificially from tanning beds, is made up of rays which can penetrate the skin and cause permanent damage. Sunlight is the main source of UV radiation exposure, so all individuals with increased sun exposure are potentially at risk for developing sun damaged and resultant precancerous skin. Indoor tanning beds tend to be even more dangerous, however, as they expose individuals to higher levels of radiation. When UV rays reach the skin’s inner layer, they can damage the DNA. If the body is unable to repair this damage, the cells can begin to divide and grow uncontrollably. 

Viral infections

Certain viral infections, such as the human papiloma virus, can also lead to the development of precancerous skin. Such viruses have genes that affect growth-regulating proteins of infected skin cells. This can cause skin cells to grow uncontrollably and stay alive for longer than usual, resulting in precancerous skin.

Genetic conditions

Individuals with xeroderma pigmentosum (XP) are at a high risk for developing skin cancer. XP is a rare, autosomal recessive condition that results from a genetic mutation affecting one’s ability to repair DNA damage. Individuals with XP also experience intolerance to light (photophobia), severe solar sensitivity, pigmentary changes on the skin, and skin dryness (xerosis). Because of their inability to repair sun damaged DNA, individuals with XP often develop cancers on sun-exposed areas of their skin and eyes.

How do you diagnose precancerous skin?

To diagnose precancerous skin, a detailed medical history and examination of the skin is necessary. When physical examination cannot clarify the diagnosis between precancerous skin lesions and skin cancer, a tissue sample (biopsy), can help determine the diagnosis. Different types of biopsies, such as shave biopsies (which are preferred for superficial lesions), or punch biopsies (ideal for deeper lesions), can be performed by board-certified dermatologists.

What do precancerous skin cells look like?

Under a microscope, the appearance of precancerous skin cells depends on the specific type of lesion. 

When looking at non-precancerous skin, one will see that the epidermis is made up of multiple layers of developing keratinocytes, which are flat cells named after the keratin protein that they’re filled with. Keratinocytes start their life at the lowest layer of the epidermis called the basal layer, which is made up of a single layer of cells that continually divide and produce new keratinocytes. These new keratinocytes then migrate upwards to form the other layers of the epidermis.

In the case of AK, the keratinocytes of the basal layer appear atypical, meaning they do not resemble those of the other non-affected cells. With Bowen disease, the keratinocytes at every layer of the epidermis appear atypical. On the other hand, actinic cheilitis and leukoplakia present with a thickened layer of keratin in the skin. Similar to AK, actinic cheilitis also presents with atypical keratinocytes in the basal part of the epidermis.

How do you treat precancerous skin?

Treatment options for precancerous skin growths usually depend on the number and location of affected areas. Most mild cases require the watch-and-wait technique, which refers to active surveillance through skin cancer screenings by board-certified dermatologists. In more severe cases, medications could be applied directly on the skin in the form of creams or gels, such as 5-fluorouracil (5-FU). For small and localized lesions, healthcare professionals may suggest photodynamic therapy, which combines light energy and specific medications to destroy the precancerous tissue. 

With more aggressive lesions, surgical removal may be suggested through cryosurgery, which uses extreme cold temperatures to destroy the cancerous tissues, or through radiofrequency ablation, which uses high frequency electric currents to remove affected tissues and stop any associated bleeding. 

In addition, adequate sun protection, such as the use of sunscreen lotion, is also highly recommended in order to limit the progression and recurrence of precancerous lesions.

What are the most important facts to know about precancerous skin?

Precancerous skin consists of several changes to the DNA of skin cells that can potentially lead to skin cancer. It can arise from personal characteristics, exposure to UV rays, certain viral infections, and some genetic conditions. Precancerous skin lesions can often vary in presentation, while some are not visible at all. These lesions often require diagnosis by board-certified dermatologists. Treatment for precancerous skin depends on the location and severity of the lesions, and can range from active surveillance to local treatment and removal of the affected area. In order to prevent further development of precancerous skin, adequate sun protection is highly recommended.

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Related links

Actinic keratosis
Skin anatomy & physiology
Skin cancer

Resources for research and reference

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