Carcinoma: basal cell and squamous cell carcinoma

Carcinoma: basal cell and squamous cell carcinoma

Skin cancer is the most common type of cancer in the US, and carcinoma is one form of the disease. Over 3.3 million people are treated for over 5.4 million cases of non-melanoma skin cancer in the US each year.11

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'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

  • Melanoma
  • 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

  • Burned
  • 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

On the next page, we look at the symptoms of basal cell carcinoma and squamous cell carcinoma and how they are diagnosed. On the final page we discuss the available treatments for carcinoma, prevention and self-examination methods.

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Basal and Squamous Cell Carcinoma (Video Medical And Professional 2020).

Section Issues On Medicine: Disease