What is Skin Cancer?

By Dr Ananya Mandal, MD

Skin cancer is the most common type of cancer among light skinned individuals. It is the commonest cancer in the United States and in Australia. Each year, about one million people are diagnosed with this cancer. In 85 percent of these cases, the skin damage leading to the cancer occurs before an individual is 18.

What is cancer?

Every cell in the body has a tightly regulated system that controls its growth, maturity, division and ultimately death. The blueprint of a cell’s function lies within the DNA of the cell. When there is damage to the DNA the cells begin to divide and grow without control. The mass of extra cells may produce a tumor that can be non-malignant or benign or non-cancerous. The tumor may also be cancer.

Normal functions of the skin

Skin is the largest organ in the body with numerous functions. It covers the internal organs and protects them from heat and light, injury and infection. The skin also controls body temperature by sweating and perspiration and stores water, fat and vitamin D. The skin is made up of two layers:-

  • Epidermis or outer layer of skin – this is made up mostly of fat and scaly squamous cells. Beneath these cells are round basal cells. The deeper parts also contain melanocytes. These cells produce melanin that gives skin its color.
  • Dermis or inner layer of skin – This layer lies deeper within and contains blood and lymph vessels, hair follicles and glands. There are glands that produce sweat to maintain the body temperature. There are also glands that produce sebum, an oily substance that keeps the skin from drying. These secretions reach the skin’s surface through small openings called pores.

What is skin cancer?

In skin cancer the cancer begins in cells that make up the skin. Skin cancers are named for the type of cells where the cancer starts. There are three types of skin cancers:

  • Basal cell carcinoma - These begin in parts of the skin that have been exposed to excessive harmful UV rays of the sun. These are slow-growing and rarely spread to other parts of the body. More than 90 percent of all skin cancers found in Americans are basal cell carcinomas.
  • Squamous cell carcinoma - These are also seen in areas exposed to excessive sunlight. These can also be found on parts of the skin not exposed to the sun. This type sometimes spreads to other organs inside the body.
  • Melanoma - This is the most dangerous type of skin cancer. It commonly spreads to other major organs like liver, lungs, brain and bones. It is however much less common than the other types. Melanoma begins in melanocytes.

Who is at risk of skin cancers?

Some of the risk factors for skin cancers include:-

  • Light or fair complexion, especially blonde, red or light-brown hair and blue, green or gray eyed individuals. Dark skinned individuals may develop melanoma.
  • Those with an easy tendency to burn in the sun or tan little or not at all. Early history of bad sunburns or scars from previous burns.
  • Prolonged sun exposure - especially during childhood.
  • Early history of skin cancer.
  • A family history of skin cancer especially melanomas.
  • More than normal number of moles (above 50 in number).
  • A history of atypical nevi or abnormal moles.
  • Those undergoing therapies like immunosuppressive therapy, photosensitive therapies etc.

Reviewed by , BA Hons (Cantab)

Further Reading

Last Updated: Jan 21, 2013

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