Virginia Commonwealth University

VCU Massey Cancer Center

Facts and anatomy

According to the latest statistics available from the National Cancer Institute and the Centers for Disease Control and Prevention:

  • Skin cancer is a malignant tumor that grows in the skin cells and accounts for 50 percent of all cancers.
  • Although exposure to the sun’s ultraviolet rays is said to be the most important factor in the cause of skin cancers, about 70 percent of American adults do not use sun-protection measures
  • Most skin cancers appear after age 50, but skin damage from the sun begins at an early age. Therefore, protection should start in childhood to prevent skin cancer later in life.

In addition, consider the following statistics from the American Academy of Dermatology:

  • Basal cell carcinoma accounts for more than 75 percent of all skin cancers in the U.S.
  • Both basal cell and squamous cell carcinomas have a 95 percent cure rate when detected and treated early. 
  •  Skin cancer incidence rates are 10 times higher for Caucasians than for African Americans. However, people with dark-pigmented skin can develop melanoma, particularly on the palms of the hands, on the soles of the feet, under the nails and inside the mouth.

Anatomy of the skin 

The skin is the body’s largest organ, covering the entire body. In addition to serving as a protective shield against heat, light, injury and infection, the skin also:

  • Regulates body temperature
  • Stores water and fat
  • Is a sensory organ 
  • Prevents water loss 
  • Prevents entry of bacteria

Throughout the body, the skin’s characteristics vary (i.e., thickness, color, texture). For instance, the head contains more hair follicles than anywhere else, while the soles of the feet contain none. In addition, the soles of the feet and the palms of the hands are much thicker.

The skin is made up of the following layers, with each layer performing specific functions:

  • Epidermis
  • Dermis 
  • Subcutaneous fat layer

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Epidermis

The epidermis is the thin outer layer of the skin which consists of the following three parts:

  • Stratum corneum (horny layer) – consists of fully mature keratinocytes, which contain fibrous proteins (keratins). The outermost layer is continuously shed. The stratum corneum prevents the entry of most foreign substances as well as the loss of fluid from the body.
  • Keratinocytes (squamous cells) – just beneath the stratum corneum, contains living keratinocytes (squamous cells), which mature and form the stratum corneum. 
  • Basal layer – the deepest layer of the epidermis, containing basal cells. Basal cells continually divide, forming new keratinocytes, replacing the old ones that are shed from the skin's surface.

The epidermis also contains melanocytes, which are cells that produce melanin (skin pigment).

Dermis

The dermis is the middle layer of the skin. The dermis contains the following:

  • Blood vessels
  • Lymph vessels 
  • Hair follicles 
  • Sweat glands 
  • Collagen bundles 
  • Fibroblasts 
  •  Nerves

The dermis is held together by a protein called collagen, made by fibroblasts. This layer also contains pain and touch receptors.
Subcutis The subcutis is the deepest layer of skin. It consists of a network of collagen and fat cells, helps conserve the body’s heat and protects the body from injury by acting as a “shock absorber.”

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