Skin – Tissue and Systems

This article describes the bodily systems involved with the skin cancer named melanoma.  Despite being a rare cancer, melanoma is responsible for a relatively large portion of cancer deaths.  Melanoma is among the top ten most common causes of death from cancer for both men and women in the United States.  Non-melanoma skin cancers are much more common but it is very rare to have serious illness or death from these types.

Melanoma is a cancer of the skin.  The skin is composed of several layers and many different types of cells.  The cells that are responsible for pigment production are called melanocytes.  The skin has two basic layers and several sub-layers.  The skin is primarily composed of the epidermis and dermis.  The epidermis is thin and the outermost layer.  This layer is made of scale like cells called stratified squamous epithelium.

The layers of the skin also house nerves for sensation and the receptors for each nerve.  There are different types of receptors for light touch, pain, and temperature sensations.  Other structures within the skin include sweat glands, hair follicles, small muscles for movement of hair and pores, pigment making cells (i.e. melanocytes) and white blood cells to fight infection.  The epidermis has several subdivisions as well.

Beyond the epidermis is the deeper dermis layer of skin.  This layer has many of the same structures that are in the epidermis.  This layer has more blood vessels to supply the rest of the skin.  The dermis is divided into several layers also.

The skin rests on loose connective tissue known as fascia.  The skin has a deep fatty layer that connects it with the underlying structure which is usually muscle but may be bone or other soft tissue.  The skin is commonly referred to as the largest organ of the body.  The skin is extremely important for health and bodily function.  The main job of the skin is to provide protection from the outside world.  Protection for foreign substances and germs is provided by the skin as a mechanical barrier.  The skin also protects from excessive heat or water loss.  This is why certain injuries or diseases such as a severe total body burn place the body in such a bad predicament.  With large amounts of skin loss, we become quickly dehydrated and have difficulty staying warm.  Infection becomes a big problem as well.

The other key function provided by the skin is help with vitamin D production.  Vitamin D is converted into its active form by a change in its structure from solar energy.  Vitamin D is essential to calcium metabolism and bone health as well as several other important bodily functions.

Unfortunately, societal trends and pressures have influenced many people to seek excessive sun light to have a “tanned” look.  The skin does a great job of blocking most harmful solar radiation.  The skin is sensitive to this radiation and over time this type of exposure can cause damage to the DNA of skin cells.

The layers of the skin, like all areas of the body, will develop excess fluid from blood flow.  This extra-cellular water is called lymph fluid.  This fluid is transported back to the blood via lymph vessels.  The lymphatic fluid is processed and screened for foreign material such as bacteria in the lymph nodes.  These transport vessels are also one possible mechanism for the spread of cancer cells such as melanoma.  Unfortunately, many melanomas have already spread to lymph nodes by the time they are diagnosed.

The skin has several different cell types and thus can produce several different kinds of skin cancer.  The commonest skin cancers are basal cell carcinoma and squamous cell carcinoma.  There are also many other spots or bumps that can appear on the skin that are not cancer but are considered a normal part of aging.

Some examples of benign (non-cancerous) skin lesions include: acne, keloids, seborrheic keratosis, skin tags, and pyogenic granuloma.  The appearance of these many different kinds of skin spots can be confusing at times, even for a physician.  The purpose of reviewing the basic structure and function of the skin is to better appreciate the symptoms and signs of a particularly dangerous cancer such as melanoma.

The key to recognizing a potential melanoma is to be aware of “red flags” or key warning signs of melanoma.  The most important part of melanoma screening is prevention.  Healthy skin is much less likely to develop melanoma.  There are certain genetic conditions that increase the risk for developing melanoma such as melanoma dysplastic nevus syndrome or xerodermapigmentosum.  Having previous family members with a melanoma seems to increase the risk as well.  The most well established risk factor for melanoma is exposure to sunlight, particularly the ultraviolet B radiation.  Minimizing direct sun exposure, use of proper protective clothing and sunblock lotion are all recommended.  Persons with fair skin or red hair are at a much higher risk for development of melanoma.

Periodic inspection of the skin is important.  A change in a previous mole or skin lesion, one that appears irregular, ulcerates or bleeds are all suspicious for cancer.  The key step in addition to prevention is to bring a suspicious skin lesion to the attention of your doctor.  Periodic surveillance or taking a sample of cells from the mole are the two main strategies to deal with concerning moles that might be cancer.

REFERENCES:

  1. Townsend Jr, CM; Beauchamp RD; Evers BM; Mattox KL. (2008) Townsend: Sabiston Textbook of Surgery, 18th ed.  Chapter 30.  New York, NY: Saunders.
  2. www.cancer.gov/cancertopics/types/melanoma
  3. www.nlm.nih.gov/medlineplus/melanoma.html
  4. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.