Skin cancer: Types, Causes, Symptoms, staging, Diagnosis, Treatment and Prevention

Skin cancer is the most common of all human cancers which originate from the cells of the epidermis, the superficial layer of the skin. Mostly these are cancerous or malignant and the growth of cancer cells in the skin is uncontrolled.

Updated: June 16, 2022

Skin cancer is the most common of all human cancers which originate from the cells of the epidermis, the superficial layer of the skin. Mostly these are cancerous or malignant  and the growth of cancer cells in the skin is uncontrolled.
Cancer occurs when normal cells undergo a transformation during which they grow abnormally and multiply without normal controls. The cells multiply and form a mass called a tumor which are often referred to as skin lesions when occurs in skin. If they are composed of malignant cells and invade neighboring tissues because of their uncontrolled growth, these are said to be cancerous.
Tumors may also travel to remote organs via the bloodstream or lymphatic system. This process of invading and spreading to other organs is called metastasis. The oxygen and nutrients the normal cells need to survive and function along with the space will be occupied by maligant cells which interfear with the function of normal cell.

Types of Skin cancer:

Skin cancers are of three major types:

  • basal cell carcinoma (BCC),
  • squamous cell carcinoma (SCC),
  • melanoma

Basal Cell Carcinoma or BCCs:

BCCs are the most common type of skin cancer which are unlikely to spread to other parts of the body. They may be locally disfiguring if not treated early. Basal cell carcinoma is a slow growing cancer and usually shows on skin as a raised, pearly or waxy pink bump, often having a dimple in the middle. It can also appear translucent with blood vessels near the skin's surface. These appears most common in the head and neck.

Squamous Cell Carcinoma or SCC:

SCC originate from skin cells in the outer layer of the epidermis. It is typically more aggressive than basal cell carcinoma and can spread to other body parts if left untreated. Typically on sun exposed areas such as the hands, head, neck, lips, and ears it appears as red, scaly, and rough skin lesions. Similar red patches may be squamous cell carcinoma in Bowen's disease, the earliest form of squamous cell cancer.
Actinic keratosis is a patch of red or brown, scaly, rough skin, which can develop into any kind of skin cancer, but most commonly develop in to a squamous cell carcinoma.
Actinic keratosis, also known as solar keratosis, appears as a red or pink rough patch of skin on sun-exposed areas of the body. They are caused by exposure to UV light in sunlight. This is the most common form of precancer and can develop into squamous cell carcinoma if left untreated.


Malignant melanoma is a highly aggressive cancer that tends to metastasize relatively early and aggressively, thereby spreading to other parts of the body. These cancers may be fatal if not found and treated early. It originates from the pigment producing skin cells or melanocytes.
A nevus is a mole, and dysplastic nevi are abnormal moles. Over time these can develop into melanoma. Moles or nevi are simply growths on the skin which are very common. It is usual to have 10 to 40 moles on their body for most people.
Moles can be flat or raised or some begin as flat and become raised over time. The surface is usually smooth. These are round or oval and no larger than one fourth inch across which are usually pink, tan, brown, or the same color as the skin.
A melanoma can be suspected if a mole has any of the abnormal features such as:

  • Asymmetrical shape
  • Border irregularities
  • Color that isn't consistent
  • Diameter larger than 6 millimeters
  • Evolving size or shape

A mole that looks different from the others should be examined by your healthcare professional.
Dysplastic nevi are often not cancerous, but they can become cancer. Usually people with dysplastic nevi often have 100 or more in numbers. These are usually irregular in shape, with notched or fading borders.
Dysplastic nevi may be flat or raised, and the surface may be smooth or rough. These are often large, at least one fourth inch across or even large which are typically of mixed color, including pink, red, tan, and brown. People with many dysplastic nevi are more likely to develop melanoma, either within an existing nevus or on an area of normal appearing skin.
The four major types of melanoma include:

Superficial spreading melanoma:

This is the most common type of melanoma. Lesions are usually flat, irregular in shape, and contain varying shades of black and brown which can occur at any age.

Lentigo maligna melanoma:

This type of melanoma usually affects the elderly involving large, flat, brownish lesions.

Nodular melanoma:

It can be dark blue, black, or reddish-blue, but can be colorless. It usually starts as a raised patch.

Acral lentiginous melanoma:

This is the least common type of melanoma which typically affects the palms, soles of the feet, or under finger and toenails.
Some other rare forms of skin cancer include lymphomas, Merkel cell cancers, and cancers of other tissue in the skin, including sarcomas as well as hair and sweat gland tumors.
Kaposi sarcoma is another type of cancer that involves skin lesions. These can appears as brownish-red to blue in color and usually found on the legs and feet. It affects the cells that line blood vessels close to the skin. This cancer is caused by a type of herpes virus, typically in patients with weakened immune systems such as those with AIDS.

Causes of Skin Cancer:

The most frequent cause of skin cancer is ultraviolet (UV) light exposure which generates from sunlight. Other important causes of skin cancer include the following:

  • Use of tanning booths
  • Immunosuppression which is caused by impairment of the immune system. The immune system protects the body from foreign entities, such as germs or substances that cause an allergic reaction. This suppression may occur as a consequence of some diseases or can be due to medications prescribed to combat conditions such as autoimmune diseases or prevent organ transplant rejection.
  • Exposure to unusually high levels of X-rays
  • Contact with certain chemicals-arsenic such as miners, sheep shearers, and farmers, hydrocarbons in tar, oils, and soot may cause squamous cell carcinoma

The following people are at the greatest risk:

  • People with fair skin, especially types that freckle, sunburn easily, or become painful in the sun
  • People with light hair and blue or green eyes
  • Those with certain genetic disorders that deplete skin pigment such as albinism, xeroderma pigmentosum
  • People who have already been treated for skin cancer
  • People with numerous moles, unusual moles, or large moles that were present at birth
  • People with close family members who have developed skin cancer
  • People who had at least one severe sunburn early in life

Basal cell carcinomas and squamous cell carcinomas are more common in older people. Melanomas can occur at any age. It is most commonly diagnosed between 55 and 75 years of age, but about one third occur before the age of 50. For example, melanoma is the most common cancer that occurs in people younger than 30.

Symptoms of Skin Cancer:

A basal cell carcinoma (BCC) usually appears like a raised, smooth, pearly bump on the sun exposed skin such as the head, neck, or shoulders which are most often mistaken for a sore that does not heal. Small blood vessels may be visible within the tumor. A central depression with crusting and bleeding or ulceration develops frequently.
A squamous cell carcinoma (SCC) is commonly appears as red, scaling, thickened patch on sun exposed skin which may develop into a large mass if left untreated.
Bleeding and ulceration also may occur in SCC.
Initially the majority of malignant melanomas are brown to black pigmented lesions. Change in size, shape, color, or elevation of a mole are the warning signs of its development.
The appearance of a new mole during adulthood, or new pain, itching, ulceration, or bleeding of an existing mole should all be checked by a healthcare professional.

Diagnosis of Skin Cancer:

The dermatologist will examine any moles or other lesion that is worrisome and, in many cases, the entire skin surface.
Lesions that are difficult to identify, or are thought to be skin cancer can be diagnose by biopsy. A sample of skin will be taken so that the suspicious area of skin can be examined under a microscope. It is always be done in the dermatologist's office. You will probably undergo further testing to determine the extent of spread of the disease if a malignant melanoma is found during biopsy. This may include blood tests, a chest X-ray, and other tests as required.

Staging for Skin cancer:

For basal cell carcinoma there is no specific staging system. It is considered as more serious tumor if the tumor is wider than 2 cm. Basal cell carcinomas of the ears, nose, and eyelid may also be of more concern, regardless of the size.
For squamous cell carcinoma there is a staging system. Tumors that are thicker than 2 mm or larger that has invaded the nerve structures of the skin, occur on the ear, and have certain worrisome characteristics under the microscope are of more concern.
The cancer is considered as a dangerous tumor if the tumor has spread to a site at some distance from the primary tumor.

Treatment for Skin Cancer:

There are several effective ways of treating skin cancer. Depends on the location and size of the tumor, the microscopic characteristics of the cancer, and the general health of the patient, the choice of therapy can be made.

Topical medications:

Some creams, gels, and solutions can be used which including imiquimod in the case of superficial basal cell carcinomas. This works by stimulating the immune system of the body causing it to produce interferon which attacks the cancer. Fluorouracil (5-FU), a chemotherapy drug can also be used. Side effects of these topical treatments include redness, inflammation, and irritation. But not necessarily everyone will experience these. The main drawback of topical medications is that there is no tissue available to examine to determine if the tumor has removed completely.

Destruction by electrodessication and curettage (EDC):

The procedure is done by giving a local anesthetic to the tumor area to make it numb. Then the area is repeatedly scraped with a sharp instrument, and the edge is then cauterized with an electric needle. This method is fast, easy, and relatively inexpensive. However, the scar is often somewhat unsightly, and there is a chance of recurrence.

Surgical excision:

In this procedure also the area around the tumor is numbed with a local anesthetic. A football shaped portion of tissue including the tumor is then removed and then the wound edges are closed with sutures. Skin grafts or flaps are needed to close the defect for very big tumors. There is a greater chance of cure rate. The surgical specimen can be examined to be sure that the whole tumor is successfully removed which is one of the main advantage of this procedure. It is a more complicated procedure and is more expensive compared to EDC. But the scar produced during the procedure is usually more cosmetically acceptable than that of the EDC procedure. 

Mohs micrographic surgery:

The surgeon removes the visible tumor with a small margin of normal tissue after he site is locally anesthetized. The tissue is immediately evaluated under a microscope and areas that are suspected to be residual microscopic tumor involvement are re-excised. The margins are re-examined and the cycle continues until no further tumor is seen. This is a more complicated and expensive option. This is the treatment of choice for tumors

  • where normal tissue preservation is essential,
  • where the tumor margins are poorly defined,
  • in tumors that have been previously treated and have recurred,
  • in certain high-risk tumors.

Radiation therapy:

A high dose of radiation of ten to fifteen treatment sessions are given to the tumor and a small surrounding skin area. For person who are not suitable for any surgical procedure for any reason, this form of treatment can be an option. There is no cutting involved in this method which is a great advantage of radiation therapy. The disadvantages of this method include:

  • This is an expensive alternative.
  • The treated area cannot be tested to make sure the whole tumor is gone
  • Radiation scars look worse over time.
  • Therefore it is usually reserved for elderly patients.

Other types of treatments:

  • Cryosurgery where tissue is destroyed by freezing,
  • Photodynamic therapy (PDT) in which medication and blue light is used to destroy the cancerous tissue,
  • Laser surgery to vaporize or ablate top layer of the skin and destroy lesions,
  • Oral medications such as vismodegib and sonidegib

Prevention for Skin Cancer:

Many skin cancers can be prevented by avoiding triggers that cause tumors to develop which include:

  • Limit sun exposure. Attempt to avoid the intense rays of sun between 10 a.m. and 2 p.m.
  • Apply sunscreen frequently. Use a sunscreen with sun protection factor (SPF) of at least 15 both before and during sun exposure. Select products that block both UVA and UVB light. Check the label before purchasing the product.
  • Wear long sleeves and a wide-brimmed hat if you are likely to sunburn.
  • Avoid artificial tanning booths.
  • Conduct periodic skin self-examinations.

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