There are a number of forms of skin cancer, with non-melanoma skin cancer the most common. Each year in the US, 2.8 million people are treated for basal cell carcinoma, and there are over 700,000 cases of squamous cell carcinoma. More skin cancers are diagnosed annually in the US than all other cancers combined.1,2,11
Learn all about carcinoma and its management with the easy-to-understand information on these pages.
You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Here are some key points about carcinoma. More detail and supporting information are in the body of this article.
- One in five Americans will develop skin cancer in their lifetime.
- There two main types of carcinoma are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC).
- Both BCC and SCC are much more common than melanoma and are referred to as non-melanoma skin cancer.
- Squamous cell carcinoma is less common than basal cell carcinoma but more likely to spread (metastasize).
- The incidence of SCC has increased by up to 200% in the past three decades in the US.
- Carcinoma can affect the surface tissue (epithelium) of numerous other organs.
- Diagnosis is made after a patient presents with signs and symptoms to a clinician, who will then take a history, conduct an examination and arrange a biopsy.
- Treatments are similar to those for other types of cancer and include surgical removal, drug therapy and other locally applied treatments and radiation therapies.
- The main preventive measure against carcinoma is to reduce exposure to ultraviolet light, by avoiding peak daylight and wearing protective clothing and effective sunscreen, for example.
- Some risk factors are unavoidable, such as rare syndromes and a number of conditions and medications that result in immunosuppression.
- Regular self-examination of the skin is an important tool in detecting the first signs of skin cancer so as to access prompt and effective treatment.
What is carcinoma?
Carcinoma affects cells located in the epidermis, the top layer of the skin.
Carcinomas are the two most common forms among three main types of skin cancer:2
- Basal cell carcinoma
- Squamous cell carcinoma.
The carcinomas are also known as non-melanoma skin cancers.3 A carcinoma can affect organs other than the skin because it is a cancerous tumor of epithelial tissue - tissue that forms the surface of the skin, digestive tract, blood vessels and various other organs.4
Every year in the US, over 3 million people are treated for basal cell or squamous cell skin cancer, compared with a much smaller number treated for melanoma.
Around 74,000 people are estimated to be diagnosed with melanoma in 2015, of which just under 10,000 are expected to die. While melanoma accounts for less than 2% of skin cancer cases, it accounts for the majority of deaths from skin cancer.11
Basal cell skin cancer accounts for around three-quarters of all skin cancers and is several times more common than the squamous cell type. A rare form of skin cancer also exists called Merkel cell carcinoma.2
Most cases of carcinoma appear after the age of 50.5 Some 40-50% of Americans over 65 will have either BCC or SCC at least once.11
What is basal cell carcinoma?
Basal cell carcinoma arises in, unsurprisingly, the basal cells found deep in the skin's epidermis, below the squamous cells. These rounder skin cells form the base layer of the epidermis that meets the dermis.2
Doctors who suspect that a patient has basal cell carcinoma - which is unlikely to spread - will refer the patient for further assessment. If they suspect squamous cell carcinoma - which is more likely to spread - they will provide a more urgent referral.5,6
What is squamous cell carcinoma?
Squamous cells make up most of the epidermis - the top layer of the skin. These are the flat, scale-like cells that are affected in squamous cell carcinoma.2,3,5
Doctors who suspect a patient has squamous cell carcinoma will offer a more urgent referral than for a patient with suspected BCC, as SCC is more likely to spread.5,6
Causes of carcinoma
As well as causing sunburn, overexposure to UV light is the main cause of carcinoma.
Exposure to ultraviolet (UV) radiation - from sunlight - is the major cause of carcinoma and other skin cancers. Some people are more vulnerable than others to the effects of sunlight on cancer development, and additional UV exposure from tanning beds and UV drying lamps in nail salons, for example, can add to this risk.1,5,7
UV radiation can lead to skin cancer by causing damage to the DNA in skin cells, leading to mutations during cell division.3
A list of risk factors for carcinoma is given in the section on prevention, with a number of strategies listed to avoid overexposure to UV light.
Actinic keratosis (precancerous changes in skin cells) is a risk factor for squamous cell carcinoma and affects more than 58 million Americans. 11 Without treatment, this condition may develop into skin cancer. Actinic keratosis is defined as a flat, scaly growth on the skin, typically on the most sun-exposed areas.5,8
While UV radiation is the major risk factor for squamous cell carcinoma, this form of cancer can also develop when skin has been:5,8
- Damaged by chemicals
- Exposed to X-ray radiation.
Basal cell carcinoma can also develop in people who were exposed to X-ray radiation as children, although this is a much less common cause of BCC than UV radiation.5
Symptoms of carcinoma
Basal cell and squamous cell carcinomas are both skin tumors and have some shared characteristics. However, these skin lesions can be highly variable in appearance, making it important not to rely on a specific description before going to get a lesion examined.8
Carcinomas can also be flat areas of skin that show little difference from normal skin, so any lesion, particularly ones that fail to heal, is worth monitoring.1
A lump or lesion can go unnoticed until it is relatively large because there may be no noticeable symptoms aside from its appearance. Large tumors at this stage may itch, bleed or be painful.1
Basal cell carcinoma typically starts out as a shiny papule - a small red or pink lump that enlarges slowly.1,3,8
A shiny, pearly or waxy-looking border may form after a few months or years. A raised edge may ring a central ulcer, and abnormal-looking blood vessels can be visible.1,3,8
Basal cell carcinomas may emerge as blue, brown or black areas, pale or yellow areas similar to scars, or pink growths. Given this variability and the need for treatment, obtaining an accurate diagnosis from a doctor is important.1,3,8
Basal cell carcinomas can have a scaly appearance, and there is often recurrent crusting or bleeding. The crusting over may look like healing, but sores can return. Doctors often see basal cell carcinoma because the patient has had a sore - triggered by shaving, for example - that fails to heal.1,3,8
While they often (but not always) appear in sun-exposed areas of skin, squamous cell carcinomas have a highly variable appearance. As a result, any non-healing lesion or new growth should be considered suspicious.1,3,8
Squamous cell carcinomas typically appear as persistent, thick, rough, scaly patches or as a firm pink lump with a flat, scaly and crusted surface. These lesions may bleed if bumped, scratched or scraped, and while they may look like warts, they can also appear as open sores with a crusted surface or raised edge.
Changes in pre-existing skin growths or sores, or the development of a new growth should be assessed by a physician.
Signs of carcinoma and other skin cancers can be detected through regular self-examination.
A daily pill known as sonidegib (branded Odomzo), marketed by Novartis, became available in July 2015 in the US for the treatment of locally advanced basal cell carcinoma.
A study in 2012 of over 110,000 people found a link between caffeine intake and a lower risk of developing basal cell carcinoma.
A meta-analysis published in JAMA's Archives of Dermatology in June 2012 suggested smoking was linked to a higher risk of squamous cell carcinoma.
Tests and diagnosis
The first step in the diagnosis of any form of skin cancer is presentation of signs and symptoms to a doctor, who will:1-3,5,8
- Take a history by asking questions about such things as when and how a skin lesion first appeared and how it might have developed, and whether there is history of associated conditions such as sunburn
- Conduct an examination of the skin lesion, recording its size, shape, texture and other physical attributes. They may also take a photo for review by a specialist or to record its present size and appearance for later comparison. The doctor will often look all over the body for additional skin symptoms.
Suspected cases of squamous cell carcinoma are referred urgently for specialist investigation and treatment because they may spread. Suspected basal cell tumors are referred non-urgently as they are less likely to spread.6
All suspected cases of skin cancer are biopsied. Skin biopsy takes four common forms, all aiming to take a sample of the suspected tumor for laboratory assessment:1,2
- Shave biopsy - using a sharp surgical blade, the top layers of cells are shaved off, usually down to the dermis but sometimes deeper, often resulting in bleeding that can then be cauterized
- Punch biopsy - a sharp, hollow surgical tool - a bit like a tiny cooker cutter - removes a circle of skin to below the dermis. The resulting wound may need a single suture
- Incisional biopsy - part of the growth is removed with a scalpel, cutting away a full-thickness wedge or slice of skin, whose wound usually then needs to be stitched together with sutures
- Excisional biopsy - the whole growth and some surrounding tissue is removed with a scalpel, with the resulting wound usually requiring sutures.
The sample is sent to a pathology laboratory for histological examination under a microscope. The cells are assessed to determine whether or not they are cancerous and, if so, what type of cancer is present.1,2,8
If a skin cancer is diagnosed, the doctor will then stage the cancer - determining the extent of the disease by assessing the size, depth, extent of local invasion and whether there has been any spread to other parts of the body such as nearby lymph nodes or more distant sites. Local lymph nodes may be sampled by fine-needle biopsy for laboratory examination.1,2
Because basal cell carcinoma rarely spreads, further investigations are not usually needed, whereas testing for metastasis may be necessary in cases of squamous cell carcinoma. This further testing may be carried out with imaging such as X-ray, computerized tomography (CT), magnetic resonance imaging (MRI) or positron emission tomography (PET) scans.2
Staging may not take place until after the surgical removal of a skin tumor. Staging ranges from stage 0 to 4, with 0 representing carcinoma in situ, which affects only the top layer of the skin. Stage 4 carcinoma described a skin cancer that has spread to other parts of the body. The stages in between are dictated by lesion size, depth and any nearby invasion.2
Treatments for carcinoma
Treatment options are similar for both basal cell carcinoma and squamous cell carcinoma, although with the latter there is greater emphasis on monitoring for signs of metastasis.8
The specific treatment or treatments undertaken will depend on the size, type, stage and location of the carcinoma, in addition to factors such as patient preference and side effects. Treatment will also likely involve a number of doctors, including dermatologists and surgical, medical and radiological cancer specialists.1,3,5,8
Treatments for carcinoma include:1,3,5,8
Topical chemotherapy for carcinoma is not associated with the side effects that typically occur with systemic chemotherapy for other forms of cancer.
- Curettage and electrodesiccation - a common procedure to remove the lesion
- Surgical excision - also removes the lesion, sometimes in a procedure known as Mohs surgery
- Cryosurgery - for small tumors, a procedure using liquid nitrogen to freeze and kill cancer cells
- Topical chemotherapy or other drugs applied to the skin to kill cancer cells
- Photodynamic therapy - a treatment for basal cell carcinoma that uses a light-sensitive cream
- Radiation therapy - usually reserved for large tumors or those for which surgical removal is difficult.
Curettage and electrodesiccation for carcinoma is a common surgical procedure for treating small skin cancer lesions using a curette. The small, sharp spoon or ring-shaped instrument is used to scrape away the carcinoma.1,3,5,8
The site is then burned (desiccated) with an electric needle to remove surrounding tissue and any remaining cancer cells. The procedure may leave a small scar and may need to be repeated to ensure complete removal.1,3,5,8
Surgical excision of carcinoma is used to remove larger lesions not able to be treated by curettage. This type of procedure involves the removal of the tumor using a surgical knife.1,3,5,8
The carcinoma and surrounding skin are removed and the surgical wound is repaired with the aid of closing stitches.1,3,5,8
Mohs surgery is a microscopically controlled procedure in which tissue removal is incremental, with a microscope used to check for remaining cancer cells after each step. The tumor is removed in a thin layer initially, and further tissue is removed in increments, minimizing loss of healthy tissue and scarring. It is an increasingly popular type of surgery for cancer, especially for:1,3,5,8
- Cases with a suspected high risk of recurrence
- In areas needing minimal skin removal - near the eyes, for example.
Cryosurgery treatment for carcinoma is used for small basal cell or squamous cell carcinomas. It is a less common form of treatment than surgical removal and involves the application of liquid nitrogen to the lesion. This causes the lesion to blister and crust over before falling off in subsequent weeks.1,3,5,8
Chemotherapy and other topical drug treatments for carcinoma are applied directly to the lesion.
Other, non-chemotherapeutic, treatments include imiquimod cream (sold under the brand names Aldara and Zyclara). This is used for small basal cell carcinomas and works by encouraging the body to produce interferon, which causes the immune system to attack the tumor. Interferon may also be injected directly into the lesion.1,3,5,8
The chemotherapy option is 5-fluorouracil (Carac, Efudex, Fluoroplex and others) - a cancer-killing drug applied to the skin once or twice daily for a number of weeks. Since it is a local treatment, it is not associated with the side effects that can occur with chemotherapy for other types of cancer.1,3,5,8
Photodynamic therapy for carcinoma is sometimes used to treat basal cell carcinoma. It is a two-step therapy involving the application of a light-sensitive cream followed by exposure to a strong source of a particular wavelength of blue light. This results in the death of carcinoma cells. As the skin remains light-sensitive for the next 48 hours, it is important that patients avoid UV light during this time to minimize the risk of severe sunburn.1,3,5,8
Radiation therapy for carcinoma is - as for other forms of cancer - the use of radiation (high-energy X-rays or particles) to destroy the cancer. Radiation therapy is reserved for cases of carcinoma that are inoperable or cover a large area.1,3,5,8
Laser therapy for carcinoma involves the use of different types of lasers to destroy cancer cells. Some lasers vaporize (ablate) the skin's top layer, thus destroying lesions in the uppermost layer. Other lasers are non-ablative and penetrate the skin without removing the top layer, with some evidence of success in treating small, superficial basal cell carcinomas.
Laser therapy is not yet FDA-approved for BCC. It is sometimes used as a secondary therapy if other treatments have not been successful.
Prevention of carcinoma
There is no routine screening program for carcinoma - rather, patients can screen themselves or ask a physician to examine them.8 Look for any changes to the skin that do not resolve (see below for more on self-examination).3
UV light is the main risk factor for both types of carcinoma and so the best prevention strategy is to be sensible about sun exposure and to avoid tanning beds.3,5,8
There are three main aspects of sensible sun exposure:3,5,8
- Sun avoidance
- Protective clothing
Sun avoidance protects against carcinoma (both basal cell and squamous cell) by reducing exposure to UV light and reducing the risk of sunburn. Sun exposure should not, however, be avoided altogether; it is important to get some sun in order to maintain healthy levels of vitamin D.3
Do not get sunburnt. Reduce sun exposure by not staying in direct sunlight when it is at its hottest (go into the shade), typically between 10 or 11 am and 3 or 4 pm.3,5
Clothing can reduce the risk of carcinoma. Simple tips for dressing sensibly to avoid too much sun exposure include wearing a hat, tops with sleeves and sunglasses.1,3,5
Clothes made with sun-protective fabrics should have labels that show a UV 400 or UV protection factor (UPF) label, and tight-weave fabrics are generally more protective than loose-weave ones.1,3,5
Sunglasses should be labeled for 100% protection against both UVA and UVB radiation.3,5
Some sunscreens offer protection against carcinoma. Choose an approved broad-spectrum sunscreen and apply liberally and often to block skin exposure to UV light. Check the label to ensure that the sunscreen protects against both UVA and UVB radiation. 1,3,5 As some sunscreens are ineffective and contain suspected carcinogens, it is wise to check consumer reports to make sure you choose a safe and effective product.12
Sunbeds are a concentrated source of UV radiation and their use increases the risk of carcinoma.
Use a sunscreen that has a sun protection factor (SPF) of at least 30 and reapply it to the entire extent of exposed skin every 2 hours (and every hour when heavily sweating or going into the water; waterproof lotions are also available).3,5
Babies and young children are particularly vulnerable to sun exposure. UV light levels are more dangerous at higher altitudes and in places closer to the equator and are more persistent in places where there is sun year-round.1,3,5
The US Preventive Services Task Force state that children, adolescents and young adults aged between 10 and 24 years who have fair skin should minimize their UV radiation exposure.10
Other factors that increase the risk of carcinoma include having had skin cancer previously (and radiation treatment for any form of cancer, especially in childhood), or a family history of cancer. Further vulnerabilities include:1,5
- Having numerous, irregular or large moles, or freckles
- Tending to burn before becoming suntanned
- Having fair skin, blue or green eyes, or blond, red or light brown hair
- Autoimmune disease such as systemic lupus erythematosus
- Inherited conditions such as xeroderma pigmentosum and nevoid basal cell carcinoma syndrome (Gorlin syndrome)
- Immunocompromising conditions such as HIV infection, receiving an organ transplant or taking immunosuppressant drugs
- Medicines that make the skin photosensitive such as vandetanib (Caprelsa), vemurafenib (Zelboraf), and voriconazole (Vfend)
- Human papillomavirus (HPV) infection, particularly if there is immunosuppression.
Sunbeds increase the risk of carcinoma. Avoid using tanning beds, tanning parlors and sun lamps.3,5 Artificial tanning is more dangerous than natural sunbathing because it exposes the body to a concentrated source of UV radiation.3 Avoid the use of nail lamps when getting a manicure or pedicure as these can also increase the risk of skin cancer, especially when nail treatments are a regular occurrence.13
Self-examination to screen for carcinoma
The basic principle of screening for carcinoma - and any other form of skin cancer - is to look for skin changes that do not resolve.3 Effective self-examination of the skin includes:2,5
- Paying particular attention to areas that get regular sun exposure
- Asking a partner to check difficult-to-see areas, and using full-length and hand mirrors
- Knowing your skin. Learn how moles and marks normally look so that changes are readily noticed - taking photos can help
- Looking for any changes, whether in size, shape, color or texture
- Performing self-examination in good lighting conditions
- Getting any sores that do not heal checked by a doctor
- Working across the body systematically, from head to toe, to ensure all areas of the skin are examined
- Not neglecting any areas of the body, including the private ones
- Keeping a note of any observations and record the dates of examinations.
Treatment is likely to be more effective in cases where a patient spots skin changes early and gets help from doctors. Where the problem is found to be cancerous, early treatment dramatically improves chances of survival and reduce the likelihood of significant tissue trauma and disfigurement.5