An Overview of Skin Cancer

Skin cancer is the most common type of cancer diagnosed in the United States and can be broken down into squamous cell cancers, basal cell cancers, and melanomas, as well as some less common cancers. Symptoms may include a sore that doesn't heal, a new spot on the skin, or a mole that is changing.

At the current time, skin cancer is considered an epidemic in the United States, accounting for 50 percent of all cancers. Roughly 80 percent of skin cancer-related deaths are due to melanoma.

When doctors suspect a skin cancer during an exam, a biopsy is needed to make the diagnosis. Treatment options depend on the type and stage, with surgery to remove cancer being the most common approach. With melanomas and advanced squamous cell carcinomas, other treatments such as immunotherapy, chemotherapy, or radiation may be needed. Luckily, there are many simple things you can do to lower your risk.

3 Common Types of Skin Cancer
Verywell / Emily Roberts

Your Skin

Many people do not think of the skin as an organ, but like other organs, it has a discrete structure and many important functions. Since treatment options for skin cancer often depend on the depth of cancer, it's helpful to understand the three basic layers of the skin.

Epidermis

The epidermis is the top layer of skin and serves several functions, including protecting the interior of your body from the environment. Cells in this layer include the following, which give rise to the most common skin cancers—squamous cell carcinoma, basal cell carcinoma, and melanoma:

  • Squamous cells lie just below the outer surface of the skin.
  • Basal cells lie beneath the squamous layer and produce new skin cells.
  • Melanocytes are located in the basal cell layer of the skin and produce melanin, the pigment that gives skin its color.

Dermis

The dermis is the middle layer of skin made up of collagen and elastin. It contains hair follicles, oil-producing glands (sebaceous glands), nerves, and blood vessels.

Subcutaneous Tissues

The subcutaneous tissue contains fat, connective tissue, and larger blood vessels; the amount of this tissue varies depending on a person's weight.

Types

There are three common types of skin cancer and more than 100 less common types. Together, basal cell carcinoma, and squamous cell carcinoma are referred to as non-melanoma skin cancers

Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common form of skin cancer, accounting for 75% to 80% of these cancers. The lifetime risk of developing a basal cell carcinoma is around 30%. It was once found mostly in middle-aged or older people, but is increasingly being found in younger people. It is the most common skin cancer among Hispanics.

Basal cell carcinoma usually begins on areas exposed to the sun, such as the face, neck, and hands. It is a slow-growing cancer that rarely spreads to other parts of the body, but people with a history of BCC are at higher risk for getting a second case.

The cancer originates in the basal cell layer of the epidermis (the stratum basale). The basal cells there mutate and begin to replicate uncontrollably. As the cancerous cells grow, they can spread into the dermis, nearby lymph nodes, and may eventually invade bones. If not treated, they can damage the surrounding tissue, causing disfigurement.

Treatments are very effective when these cancers are found and treated promptly.

Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) accounts for 16 percent to 20 percent of skin cancers and occurs twice as often in men as in women. These are the most common type of skin cancers found in blacks.

Unlike basal cell carcinomas, these cancers may spread (metastasize) if they become large. It usually occurs on the face, ear, neck, lips, and backs of the hands. SCC can also begin within scars or skin ulcers on other places on the body. As with basal cell carcinoma, the available treatments are very effective if the tumor is detected while it is small and thin.

Squamous cell carcinomas have the strongest association with sun exposure.

Melanoma

Melanoma is the most feared type of skin cancer. Though less common than basal cell and squamous cell cancer, it is responsible for the majority of deaths from the disease as a whole. Melanoma may arise in normal skin but often begins in an existing mole. It is found most frequently on the back in men, on the legs in women, and on the palms of the hands, soles of the feet, and under the fingernails or toenails of people of both sexes with darker skin colors. That said, these cancers may occur anywhere, including areas of the skin that have never been exposed to the sun.

The incidence of melanoma has been rising dramatically in the United States for the last three decades. While melanoma in general is 20 times more common in whites, the incidence of cases that occur under the nails is similar for people of all skin color. In addition, the survival rate in those diagnosed is lower in black people.

The prognosis of melanoma is good when found early, but drops precipitously when it spreads to distant lymph nodes or organs, such as the bones, the lungs, the liver, and the brain. Newer treatments, however, are making a difference in survival, and even some advanced melanomas can now be controlled with these options. 

Rare Types

The other types of cancer that can arise in the skin or skin-related structures are far less common. A few of these include:

  • Merkel cell carcinoma: Merkel cell carcinomas are rare skin cancers most often found around the eye in middle-aged people. For unknown reasons, these cancers are increasing. They tend to be aggressive and spread rapidly to other parts of the body.
  • Kaposi's sarcoma: This cancer is caused by the Kaposi sarcoma herpesvirus, and is usually found in people with HIV/AIDS or who are immunosuppressed for other reasons, such as an organ transplant. It presents as large red, blue, or brown splotches around the body along with swelling that can be severe. Fortunately, it often responds well to HIV medications.
  • Sebaceous gland carcinoma: These cancers originate in sebaceous glands and occur most often in older women, around the eye.
  • Dermatofibrosarcoma protuberance: These cancers begin as a hard nodule that originates in the dermis and spreads rapidly. They are related to a gene mutation that results in overproduction of a protein known as a platelet-derived growth factor.

Skin Metastases and Other Cancers That Occur in the Skin

Sometimes, cancers that arise in other areas of the body may spread (metastasize) to the skin. Cancers most commonly associated with skin metastases include breast cancer, colon cancer, and lung cancer. When other cancers spread to the skin they are not classified as skin cancer. In fact, though the cancer may now be affecting the skin, its cells are clearly identifiable as belonging to the instigating cancer when examined under a microscope. Treatment for the cancer at play, rather than skin cancer, is needed.

Some examples of this include inflammatory breast cancer, which often begins with redness and a rash on the breast); Paget's disease, a form of breast cancer that begins on the skin of the nipples; and cutaneous T cell lymphomas (including mycosis fungoides and Sezary syndrome), which often begin as flat, red patches of skin that are extremely itchy.

Symptoms

Signs and symptoms of skin cancer may include any change that is noted on the skin, such as:

  • A sore that doesn't heal
  • A mole that is changing
  • Scaly, crusty appearing lesions
  • Pink, white, or flesh-colored lumps that appear dome-like
  • Itching

Some refer to the ABCDE (and F) mnemonic to help them recognize when a skin change could be skin cancer:

  • A stands for asymmetry: A mole or sore that is asymmetric.
  • B stands for borders. The borders of a melanoma may be irregular, notched, or blurry.
  • C stands for color. Melanomas often have more than one color or hue.
  • D stands for diameter. A mole that is larger than a pencil eraser is more likely to be a melanoma.
  • E stands for either elevation or evolution. The mole may be elevated (often irregularly) and is often evolving (changing) over time.
  • F: Though an unofficial qualifier, many add this to represent a skin change that is "funny" looking.

Causes and Risk Factors

We don't know exactly what causes skin cancer, though we have identified several risk factors. Some of these include:

  • Sun exposure (especially extensive and/or unprotected)
  • Pale skin
  • Red or blonde hair
  • Light eyes (green or blue eyes)
  • Skin that rarely tans and burns easily
  • Family and/or personal history of skin cancer
  • Having one of several genetic syndromes, such as xeroderma pigmentosum
  • Having many moles (more than 50) or having atypical moles (nevi)
  • Scars from burns or previous skin infections
  • A weakened immune system
  • Use of some medical treatments and medications, such as radiation therapy for cancer and ultraviolet light for psoriasis
  • Frequent exposure to chemicals such as tar and vinyl chloride
  • Exposure to arsenic in drinking water
  • Smoking (increases the risk of squamous cell carcinoma)

Diagnosis

Diagnosing skin cancer begins with a careful history (paying attention to symptoms and risk factors) and a physical exam. Based on the appearance of the skin lesion, a doctor may recommend a biopsy, as it can sometimes be difficult to know whether an abnormality is cancer or not based on its visible appearance. This can be even more challenging in non-white populations.

Skin Cancer Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

Doctor Discussion Guide Man

A biopsy can be done in one of several ways, including:

  • Shave biopsy: The most common if a basal cell or squamous cell carcinoma is suspected), this procedure involves numbing the skin and shaving off a piece of the lesion. A punch biopsy may also be done.
  • Incisional biopsy: An incision is made and part of an abnormality is removed to be viewed by a pathologist.
  • Excisional biopsy: In this case, the entire abnormality is removed, along with an area of surrounding tissue, for a pathologist's evaluation. This is done if a melanoma is suspected. 

If a skin cancer (melanoma and sometimes squamous cell carcinoma) is advanced, further tests are done to stage the disease and search for the presence of metastases. These may include a sentinel node biopsy, CT scans, a PET scan, or other tests depending on the location of the skin cancer.

Treatments

The treatments for skin cancer will depend on many factors, such as the type of cancer, the size and depth, and more.

Surgically removing the tumor is the most common treatment. A special surgery called Mohs surgery involves removing successive pieces of tissue and checking the margins for any evidence of cancer so that the least amount of surgery to completely remove the tumor is done. With melanomas, a large area of surrounding tissue is removed.

For more advanced tumors that have spread to lymph nodes or other regions of the body, treatments such as immunotherapy, chemotherapy, targeted therapy, and radiation therapy may be needed.

Prevention and Early Detection

There are many things you can do to prevent skin cancer or at least reduce your risk. Being careful in the sun is important, but includes more than just wearing sunscreen; using other methods of protection (such as wearing clothing and hats, and avoiding mid-day sun) should be practiced as well. Some occupational exposures may increase risk, and gloves are recommended when working with many different chemicals and substances.

Not all skin cancers can be prevented, and early detection then becomes the goal. Self-skin checks should be considered, especially for those who have any risk factors for the disease. Some people who have significant risk factors or genetic syndromes associated with a higher risk may want to consider regular visits with their dermatologist. 

A Word From Verywell

Roughly a third of people will develop some type of skin cancer in their lifetime. Being aware of the warning signs of the disease and knowing your risk factors is important in finding these cancers in their earliest and most curable stages. If you have any skin changes that concern you, don't wait—make an appointment to see your primary care doctor or dermatologist today.

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Article Sources

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