Skin cancer is the most common form of cancer in the United States. Basal cell carcinoma and squamous cell carcinoma are the two most common types of skin cancer. The third most common skin cancer is melanoma, which is more severe and causes the most deaths.

According to estimates, more than 3 million people in the U.S. receive a diagnosis of nonmelanoma skin cancer each year, and basal cell carcinoma (BCC) accounts for around 80 percent of these cases.

Unlike melanoma, BCC and squamous cell carcinoma (SCC) are common and highly treatable.

In this article, we look at the diagnosis and treatment of these carcinomas.

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Excessive exposure to the sun can lead to carcinomas, the most common type of skin cancer.

BCC and SCC are the two most common forms of skin cancer.

Carcinomas are also known as nonmelanoma skin cancers. A carcinoma is a cancerous tumor of the epithelial tissue, which is the tissue underneath the skin.

Epithelial tissue is also present in the digestive tract, blood vessels, and other organs, which means that carcinomas can affect areas of the body other than the skin.

BCC is several times more common than the squamous cell type. A rare form of skin cancer also exists called Merkel cell carcinoma.

In the vast majority of cases, people are over the age of 50 years when they receive a carcinoma diagnosis. Statistics also show that 90 percent of carcinomas occur in people with white skin.

Healthcare professionals define the different carcinomas by the type of cell in which they occur.

Basal cell carcinoma

BCC develops in the basal cells, which are round skin cells that lie deep in the skin's epidermis below the squamous cells. They form the base layer of the epidermis, which meets the dermis.

BCC is unlikely to spread, but doctors who suspect that an individual has this type of carcinoma will still refer them for further assessment.

Squamous cell carcinoma

Squamous cells make up most of the top layer of the skin, which people refer to as the epidermis. These cells are flat and scale-like.

Doctors who suspect SCC will provide a more urgent referral, as it is more likely than BCC to spread.

SCC is, however, much rarer than BCC. It is responsible for fewer than 20 percent of nonmelanoma skin cancers.

Exposure to ultraviolet (UV) radiation from sunlight is the primary cause of carcinoma and other skin cancers.

Some people are more sensitive to UV light than others and are more vulnerable to the effects of sunlight on cancer development. Additional UV exposure from tanning beds and UV drying lamps in nail salons, for example, can also add to a person's risk.

UV radiation can cause damage to the DNA in skin cells, leading to mutations during cell division and possibly resulting in skin cancer.

Risk factors

Factors and characteristics that increase the risk of carcinoma include a personal history of skin cancer and radiation treatment for any form of cancer, particularly in childhood. A family history of cancer might also contribute.

Further risk factors include:

  • having numerous, irregular, or large moles or freckles
  • a tendency to burn before getting a suntan
  • having fair skin, blue or green eyes, or blond, red, or light brown hair
  • autoimmune diseases, such as systemic lupus erythematosus (lupus)
  • inherited conditions, such as xeroderma pigmentosum and nevoid basal cell carcinoma syndrome, also known as Gorlin syndrome
  • a weakened immune system, possibly due to HIV, receiving an organ transplant, or taking immunosuppressant drugs
  • taking medicines that make the skin photosensitive, such as vandetanib (Caprelsa), vemurafenib (Zelboraf), and voriconazole (Vfend)
  • human papillomavirus (HPV) infection, particularly in people with a weakened immune system

Actinic keratosis, which consists of rough, raised growths that cause precancerous changes in skin cells, is a risk factor that is specific to SCC. These growths are the most common type of precancerous skin lesion.

Without treatment, this condition may develop into skin cancer.

While UV radiation is the leading risk factor for SCC, the following skin damage can also increase the risk of this type of carcinoma:

  • burns to the skin
  • chemical damage
  • exposure to X-ray radiation

BCC might also develop after exposure to X-ray radiation in childhood, although this is a far less common cause of carcinoma than UV exposure.

BCC and SCC are both skin tumors, and they share some characteristics. However, these skin lesions can vary in appearance.

Some carcinomas retain a flat surface and, as a result, can resemble healthy skin. Anyone with any unexpected lesions should visit a healthcare professional for a checkup and monitoring.

Other than its presence, a lump or lesion often causes no noticeable symptoms in its early stages. As a result, it might not be noticeable until it becomes relatively large, when it may itch, bleed, or cause pain.

Basal cell carcinoma

BCC typically presents as a shiny papule, which is a small red or pink lump that grows slowly.

A shiny, pearly, or waxy-looking border may form after a few months or years.

A raised edge often rings a central ulcer, and abnormal-looking blood vessels might become visible. These may emerge as blue, brown, or black areas. Alternatively, they may be pink growths or pale or yellow areas that resemble scars.

Due to this wide range of appearances, obtaining an accurate diagnosis from a doctor is essential.

BCC might appear scaly, and it often causes recurrent crusting or bleeding. When it crusts over, it may resemble a healing scab, but sores can still appear. People with BCC often seek medical advice when they discover a sore that fails to heal.

Squamous cell carcinoma

SCC typically presents as persistent, thick, rough, scaly patches or as a firm pink lump with a flat, scaly, and crusted surface.

These lesions may bleed if a person bumps, scratches, or scrapes them. While they sometimes resemble warts, they can also appear as open sores with a crusted surface or raised edge.

It is vital to seek the opinion of a healthcare professional regarding the development of any new growths or any changes in preexisting skin growths or sores.

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Diagnosing skin cancer requires physical examination and biopsy.

To diagnose any form of skin cancer, a doctor will carry out a physical examination. They will examine the skin lesion and record its size, shape, texture, and other physical attributes.

They may also take a photo of the lesion for specialist review or to record its current size and appearance for future comparisons. The doctor will often check the rest of the body for additional skin symptoms.

They will also take a medical history focusing on the lesion and any related conditions, such as sunburn.

A doctor will urgently refer suspected cases of SCC for specialist investigation and treatment due to their tendency to spread. Suspected BCC tumors do not require such urgent referral as they are less likely to spread.

If they think that a lesion may be cancerous, the doctor is also likely to perform a biopsy. There are four different types of skin biopsy, all of which involve the removal of skin tissue for laboratory assessment.

The different types are:

  • Shave biopsy: Using a sharp surgical blade, the doctor shaves the top layers of skin cells, usually as far as the dermis but sometimes deeper. This type of biopsy often results in bleeding, but it is possible to stop this by cauterizing the wound.
  • Punch biopsy: The doctor uses a sharp, hollow surgical tool that resembles a tiny cookie cutter to remove a circle of skin from below the dermis. A person may need a single stitch to close the resulting wound.
  • Incisional biopsy: The doctor removes part of the growth with a scalpel, cutting away a full-thickness wedge or slice of skin. This type of biopsy often needs more than one stitch afterward.
  • Excisional biopsy: The doctor removes the whole growth and some surrounding tissue with a scalpel. The resulting wound usually requires stitches.

After taking the tissue sample, the doctor will send it to a pathology laboratory for examination under a microscope. The pathology team will assess the cells to look for cancerous traits. If cancer is present, they will determine its type.

Further investigations are not usually necessary for people with BCC as it rarely spreads. However, individuals with SCC may need to undergo tests for cancer in other tissues.

Additional tests usually involve imaging and may include:

Staging

If a doctor does diagnose skin cancer, they will then designate it a stage. To do this, they will assess its size and depth and the extent to which it has spread to local and distant sites in the body, such as nearby lymph nodes or other organs.

To help them stage cancer, the doctor may also take tissue from lymph nodes near the site of the carcinoma. They will often use a fine-needle biopsy for laboratory examination.

Staging may not take place until after the surgical removal of a skin tumor. The stages range from 0 to 4, with 0 representing carcinoma in situ, which affects only the top layer of the skin.

Stage 4 carcinoma refers to a carcinoma that has spread to other parts of the body. The stages between describe lesion size, tissue depth, and any nearby invasion.

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Many methods are available for removing potetially harmful moles, including cryotherapy.

The treatment options for both types of carcinoma are similar, although the medical team places greater emphasis on monitoring people with SCC for signs of metastasis.

The specific treatment or treatments that the doctor recommends will depend on the size, type, stage, and location of the carcinoma. The doctor will also take into account additional factors, such as potential side effects and the preference of the individual.

Either way, treatment is likely to involve a team of healthcare professionals, including dermatologists and surgical, medical, and radiological cancer specialists.

Treatment options may include the following:

Curettage and electrodesiccation: This is a standard procedure for removing a small lesion. The doctor uses a small, sharp, spoon- or ring-shaped instrument called a curette to scrape away the carcinoma before burning the site with an electric needle.

It may take more than one round of curettage and desiccation to remove the cancer cells entirely.

Surgical excision: A surgeon removes the lesion, sometimes in a procedure known as Mohs surgery, which works better on larger lesions. During this procedure, the surgeon checks for the presence of cancer cells after removing each layer.

Mohs surgery is particularly useful in cases that require the removal of as little skin as possible, such as on lesions near the eye. Doctors will also use it on lesions with a high risk of recurrence.

Cryosurgery: For small tumors, doctors might use this procedure, which involves the application of liquid nitrogen to freeze and kill cancer cells. The lesion then blisters over and falls off in the weeks following treatment.

Topical chemotherapy: The doctor may apply chemicals or medications that kill cancer cells directly to the skin.

The chemotherapy option is 5-fluorouracil, which includes Carac, Efudex, Fluoroplex, and other medications. A doctor can apply this cancer-killing drug to the skin once or twice daily for several weeks.

As this local treatment does not reach other systems in the body, it does not cause the side effects that often occur with chemotherapy for other types of cancer.

Nonchemotherapeutic treatment options include imiquimod cream, which is available under the brand names Aldara and Zyclara. This cream is sufficient for small BCCs, and it works by encouraging the body to produce interferon, which causes the immune system to attack the tumor.

A doctor might also inject interferon directly into the lesion.

Radiation therapy: The treatment team targets large or difficult-to-remove lesions with focused radiation.

Photodynamic therapy (PDT): Doctors will sometimes use this two-step therapy to treat BCC. They will apply a light-sensitive cream to the affected area of skin and then expose it to a powerful light source. The light has the particular wavelength of blue light, which leads to the death of carcinoma cells.

As the skin remains sensitive to light for the next 48 hours, people should avoid UV light during this time to minimize the risk of severe sunburn.

Laser therapy for carcinoma: This involves the use of different types of laser to destroy cancer cells. Some lasers vaporize, or ablate, the skin's top layer, destroying any lesions that are present there.

Other lasers are nonablative and penetrate the skin without removing the top layer. There is some evidence of their success in treating small, superficial BCCs.

The U.S. Food and Drug Administration (FDA) have not yet approved laser therapy for BCC. However, doctors may sometimes use it as a secondary therapy if other treatments have not been successful.

No routine screening program is currently available for carcinoma. Instead, people can screen themselves for suspicious lesions or ask a doctor for a physical examination.

The main risk factor for both types of carcinoma is UV light. The best prevention strategy is to adopt sensible practices regarding sun exposure and avoid tanning beds.

Minimizing sun exposure: By reducing their exposure to UV light, people can reduce their risk of sunburn, skin damage, and all types of skin cancer, including carcinoma.

Although some sun exposure is necessary for maintaining healthy levels of vitamin D, which is vital for supporting skin health, sunburn increases the risk of carcinoma.

People can reduce sun exposure by seeking shade when the sun is at its peak, typically between 10 a.m. and 4 p.m.

Clothing: Clothes that protect the skin from the sun include hats with a wide brim or peak, shirts with sleeves, and sunglasses.

Clothes in sun-protective fabrics should have labels that show a UV 400 or UV protection factor (UPF). For better protection, choose tight-weave over loose-weave fabrics.

When purchasing sunglasses, check the labels for a mention of 100 percent protection against both UVA and UVB radiation.

Approved broad-spectrum sunscreens: Choose an effective sunscreen and apply it liberally and regularly to the skin to block exposure to UV light.

Check the label to make sure that the sunscreen protects against both UVA and UVB radiation.

As some sunscreens are ineffective and contain suspected cancer-causing substances, check consumer reports to ensure that a particular brand of sunscreen is safe and effective before using it.

Use a sunscreen with a sun protection factor (SPF) of at least 30 and reapply it to all exposed skin every 2 hours. Increase the application to once an hour after heavy sweating or swimming. Waterproof lotions are also available.

Infants and young children are particularly vulnerable to sun exposure. People should also be aware that UV light levels are more dangerous at higher altitudes, in places closer to the equator, and at locations that are sunny throughout the year.

The U.S. Preventive Services Task Force state that children, adolescents, and young adults aged between 10 and 24 years with fair skin should minimize their exposure to UV radiation.

Avoiding tanning beds: Tanning beds, tanning parlors, and sunlamps significantly increase the risk of carcinoma.

Artificial tanning is more dangerous than natural sunbathing because it exposes the body to a concentrated source of UV radiation. Avoid the use of nail lamps when receiving a manicure or pedicure as these might also increase the risk of skin cancer.

This advice is especially relevant for people who receive regular nail treatments.

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Self-examination is vital for identifying moles and lesions that could become skin cancer.

The basic principle of screening for carcinoma and other forms of skin cancer is to look for skin changes that do not resolve.

To be effective, self-examination of the skin should involve:

  • paying particular attention to areas of skin that get lots of sun exposure
  • asking a partner or family member to check difficult-to-see areas and using full-length and hand mirrors
  • knowing your skin and learning how moles and marks usually look to recognize any changes
  • taking photos, which can help track changes
  • checking for changes in size, shape, color, or texture
  • performing self-examination in good lighting
  • seeking medical attention for any sores that do not heal
  • working across the body systematically from head to toe to examine all areas
  • checking all areas of the body, including the more intimate ones
  • keeping a note of any observations and recording the dates of self-examinations

These measures can help people catch carcinomas early on and treat them before they spread.

Treatment is likely to be more effective in cases where a person identifies skin changes at an early stage and receives prompt medical attention.

In cases where cancer is responsible for skin changes, early treatment dramatically improves the chance of survival and reduces the likelihood of significant tissue trauma and disfigurement.

BCC has an excellent survival rate as it very rarely spreads beyond the original site. Doctors can often treat it in-office.

SCC is treatable in its early stages, and most treatments are over 90 percent effective. Mohs surgery is the most effective option, resolving SCC in 97 percent of people who receive this treatment.

However, if SCC spreads beyond the original site and reaches other systems in the body, the survival rate reduces to around 30 percent.

Early identification is essential to improving a person's outlook.

Q:

How do I tell the difference between melanoma and carcinoma?

A:

Melanoma commonly presents in the skin that gets regular exposure to sunlight, such as that on the face, neck, hands, and arms.

It is often recognizable because it causes an area of the skin to appear darker than the rest. Melanoma has this effect because it begins in cells called melanocytes, which are in the lowest layer of the epidermis and play a role in skin color.

Nonmelanoma, or BCC and SCC, are in the middle and upper layers of the epidermis respectively. Possible signs and symptoms of these carcinomas include unusual changes in the appearance of the skin, such as roughness, redness, scaliness, or areas that are small, raised, and smooth or red.

If you notice anything unusual on your skin, please visit your dermatologist for a physical examination.

Christina Chun, MPH Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.