What Is Nonmelanoma Skin Cancer?

Nonmelanoma skin cancers are a group of cancers that develop in the upper layers of the skin. They include several different types of skin cancer, but the two most common are squamous cell skin cancer (or squamous cell carcinoma) and basal cell carcinoma. 

Most nonmelanoma skin cancers are easily treatable, especially when caught early, but some are more dangerous. For most people, skin cancers are relatively preventable.

Inherited syndromes and other illnesses can increase the risk of getting these skin cancers, but excess exposure to UV light from the sun or tanning beds is the leading cause for otherwise healthy patients. Explore the major groups of nonmelanoma skin cancers.

What Is Nonmelanoma Skin Cancer?

Nonmelanoma skin cancers are the most common types of cancer. They’re so common that healthcare providers don’t even report many of them to the cancer registries, which track cancer incidence and survival rates.

Research suggests that there are 5.4 million nonmelanoma skin cancers diagnosed every year in the United States. However, some patients are diagnosed and treated for multiple lesions simultaneously or repeatedly, so the number is more like 3.3 million.

Cancers occur when cells in the body start to grow out of control due to changes in their genetic material called mutations. These changes add up over time, so cancers grow more common as you age. This is especially true for skin cancers, which are mainly due to mutations caused by cumulative UV exposure—the longer you live, the more UV exposure you get.

The mutated cells may look and act differently than the cells around them, forming lesions or tumors. Cancer cells can break away from these tumors and spread (metastasize) to other parts of the body, though this is uncommon with nonmelanoma skin cancers.

Two main types of cancer make up nonmelanoma skin cancer: basal cell carcinoma and squamous cell carcinoma. Together, they’re called keratinocyte carcinomas. They come from the outer layer of the skin, called the epidermis. The epidermis is made of three types of cells that give rise to different skin cancers:

• Basal cells are the ground floor of the epidermis, growing and dividing and creating new skin cells that eventually flatten out and flake off. These give rise to basal cell carcinomas.
• Squamous cells are the top layer of the epidermis; they’re flat cells that grow and flake off as new ones from the basal cell layer push up from below. These give rise to squamous cell carcinomas.
• Melanocytes are the pigmented cells of the epidermis which give color to the skin. They protect the deeper layers of the skin from sun damage. These give rise to melanomas.

Basal Cell Carcinoma

The most common type of skin cancer, diagnosed 4 million times per year in the United States, is basal cell carcinoma (BCC). BCCs make up about 80% of nonmelanoma skin cancers, and most can be easily treated and cured.

BCCs start in the bottom of the epidermis, where new skin cells form. If left untreated, BCCs can keep growing into deeper layers of the skin and invade nearby tissues. Metastasis to other organs is very rare, though, and these tumors typically grow slowly. 

They're common on the head (specifically the nose) and neck but can happen anywhere on the body that gets a lot of sun exposure. It’s rare for these cancers to crop up in areas of the body typically protected from the sun. 

Types

BCCs have a wide variety of appearances. They can be flesh-colored, pearl-like bumps, or pinkish patches of skin called a "pearly papule" because they're sometimes shiny.

They can be discolored, raised, or relatively flat, and sometimes scaly. They might have a central depression or ulcer and usually have red threads from tiny blood vessels running through them.

These lesions are typically sorted into five types:

Nodular:

• The most common type of BCC, they make up 60% to 80% of cases
• Commonly occur on the nose, forehead, neck, and upper back
• They can be a pink or translucent nodule, with edges that look like they’ve been rolled up
• As they grow, these lesions can develop a sore that bleeds or crusts
• They may have thin red blood vessels running along the surface
• The “micronodular” subtype is more aggressive and occurs mainly around the eyes, feels firm, and looks skin-colored or grayish

Superficial:

• These are the least aggressive BCCs, and they are about 15% of all BCCs
• They are usually found on the trunk or sun-protected sites
• They present as a grouping of dry, scaly plaques with a raised border around them that looks like a thread
• They might look like eczema or psoriasis
• Can grow to be 10 to 15 centimeters (cm) wide

Pigmented:

• This type of nodular BCC is often found in darker-skinned people
• They contain black or brown melanin pigmentation
• They are often mistaken for nodular melanoma

Diffuse:

• Includes infiltrating, morpheaform, and sclerosing subtypes
• They are more aggressive
• Occur mostly on the nose, eye angles, forehead, and cheeks
• Appear as a yellow to white plaque without a clear border around it
• Some subtypes develop sores and crust over, while others don’t
• The skin might look thinned out
• These might invade muscle, nerves, and bone
• They can have a scar-like appearance

Fibroepithelial:

• Also referred to as fibroepithelioma of Pinkus
• More common in middle-age
• Found on the torso
• Rare and unusual
• Pink smooth nodules or plaques

Risk Factors

BCCs are very common and can develop in anyone. They're more likely to occur in: 

• Light-skinned people with blue eyes and light hair
• People with regular sunburns in childhood
• Those of middle age or older
• People living closer to the equator
• Patients who have already had a BCC

Several syndromes increase your risk of a BCC:

• Gorlin-Goltz syndrome: A genetic disorder that causes basal cell carcinomas and other skin issues, along with skeletal, eye, and neurological abnormalities
• Bazex-Dupré-Christol syndrome: A very rare inherited skin disease that includes hair loss, lack of sweating, and can cause BCCs on the face as young adults
• Rombo syndrome: A very rare disease causing hair loss and skin conditions, including BCCs around age 35

Squamous Cell Carcinoma

Squamous cell carcinomas (SCCs) are the second most common skin cancer and make up the other 20% of nonmelanoma skin cancers. They develop in the outermost layer of the epidermis, the flat squamous cells that usually flake off.

They are more dangerous than BCCs because they have a greater likelihood of spreading to other parts of the body. At least a few thousand people die of metastatic SCCs each year.  Sadly, the majority of Americans—74%—are not familiar with these cancers.

SCCs are common on UV-exposed skin, like the back of the hands, the ears, neck, lips, and face, but can also develop around the genitals. They can also develop inside or around scars and recurring sores.

Types

These skin cancers might look like a scab, a red firm bump, scaly patch, or a sore that heals and reopens. They can be raised, flat, or scaly. The parts of the face that are most commonly affected with SCCs are the upper rim of the ear, face, neck, scalp, and lip.

Actinic keratosis (solar keratosis):

• Precancerous lesions, can turn into SCCs if left untreated
• Easily confused with an age spot, pimple, irritated skin, or a badly chapped lip (actinic cheilitis) 
• Look rough, dry, scaly, or sandpapery
• Usually pink/red or fleshy in color
• Don’t generally cause symptoms, but might itch, burn, sting, or feel tender or painful

Squamous cell carcinoma in situ:

• Also called Bowen's disease
• A very early form of SCC in which the cancerous cells are contained within the top layer of the epidermis
• Present as reddish patches, scalier than AKs, sometimes crusty
• Can occur near the anus or genitals, possibly caused by infection with the human papillomavirus 

Cutaneous horn:

• Hard lesions
• Take a form that looks more like an animal's horn than a zit or skin spot.

Keratoacanthoma:

• Dome-shaped tumors
• Grow quickly at first
• May go away on their own, but some continue to grow and spread

Risk Factors

The people who are most at risk for SCCs include:

• People with light skin, hair, and eyes
• Those regularly exposed to UV light
• Older people
• Men
• People who live closer to the equator
• Immune-system suppressing conditions: Organ transplant patients; those with HIV; on medications for psoriasis; arthritis; people with other auto-immune diseases
• Tobacco users
• People who previously had skin cancer or precancerous skin conditions
• Having had HPV

Other sun-sensitizing conditions also put some patients at higher risk: 

• Albinism: An inherited lack of pigment which leads to light-colored hair, skin, and eyes
• Xeroderma pigmentosum: An inherited sensitivity to the sun
• Dystrophic epidermolysis bullosa: A genetic condition that causes blistering on the extremities in mild cases but can cause complications when severe
• Epidermodysplasia verruciformis: A genetic skin disease that leads to chronic infection with HPV, the development of lesions, and a heightened risk of skin cancer
• Keratitis-ichthyosis-deafness syndrome: A rare disease linked to skin issues, eye problems, and hearing loss

Other Nonmelanoma Skin Cancers

If you notice an odd spot or growth on your skin, it’s probably a BCC or SCC. But there are also several other, much rarer, skin and skin-adjacent cancers that you should be aware of.

Merkel Cell Carcinoma

Merkel cell carcinomas (MCCs) are a rare skin cancer that arises from the Merkel cell, a special type of cell implicated in the hormone and nervous system and helps us sense light touches. Only about 2,000 cases of MCCs are diagnosed every year in the United States.

Tumors take the form of rapidly growing, painless, firm, shiny nodules that can be pink, red, or purple. They're sometimes mistaken for an insect bite, sore, cyst, stye, or pimple.

Lymphoma of the Skin

Lymphoma of the skin is an uncommon type of white blood cell cancer that happens in the skin. It’s the same as other lymphomas but arises from lymph tissue in the skin instead of in the lymph nodes or other lymph tissues.

They can look like patchy, scaly, red lesions on the skin that can be itchy. Others might feel and look like a really bad sunburn. Some types look like pimples or lumps and can develop sores.

Kaposi's Sarcoma

Kaposi’s sarcoma is cancer caused by a herpes virus in immunosuppressed patients. It develops from the cells that make up the lining of the blood and lymph vessels in the skin.

They look like painless purplish, reddish, or brown spots and can occur anywhere on the body. While they don’t usually spread or cause symptoms, they can become life-threatening if they appear in the digestive tract, lung, or liver.

Skin Adnexal Tumors

Skin adnexal tumors are a rare type of skin cancer that starts in cells of the hair follicles or other skin glands. These tumors may be benign or malignant. Malignant tumors are more likely seen in people over age 50.

Cutaneous Leiomyosarcoma

Cutaneous leiomyosarcoma is an uncommon cancer that can develop in the skin's smooth muscles, including those that control glands and hair follicles. No specific risk factor is known, but they tend to occur most often in men age 50 to 70.

A Word From Verywell

Skin cancers are generally treatable and preventable. But knowing your risk is important. If you have a personal or family history of skin cancers, or if you’re potentially at an increased genetic risk. Get screened for genetic variants if your healthcare provider advises it. 

If you have reasons to think you are at a raised risk for skin cancer, see your dermatologist regularly for check-ups. Even if you’re not at high risk, everyone should regularly check their skin for changes. Have someone else look at your scalp or the back of your neck if it's hard to see back there.

Watch for ABCDE:

• A - Asymmetry: The lesion is not symmetrical.
• B - Borders: The edges of the lesion are not clear.
• C - Color: The lesion has multiple colors, including tan, black, red, blue, or pink.
• D - Diameter: The lesion is more than 6 millimeters (0.25 inches) across.
• E - Evolution: The lesion changes in size, shape, or color.