Melanoma is a malignant cancer of the pigment cells (melanocytes) of the skin. It is of great importance to Australians for many reasons including the facts that:

• Australia has the highest incidence of melanoma in the world
  
  
• It is very frequently identifiable at a stage when simple treatment can result in complete cure

Dr Neville Davis is a Queensland surgeon with vast experience in the treatment of melanoma. He wrote

"Malignant melanoma writes its message in the skin with its own ink and it is there for all of us to see. Some see but do not comprehend."

 

The skin & melanocytes (pigment cells)

Melanocytes are found distributed in the skin:

• Scattered as individual cells at the junction of the upper (epidermis) and lower (dermis) layers of the skin. These cells produce granules of pigment in response to ultraviolet exposure (a suntan).

• Aggregated together (in groups termed naevus cells) at various depths within the epidermis and dermis.

Characteristic patterns of aggregation can usually be recognized by expert clinicians as those forming junctional, dermal, compound and dysplastic naevi (moles). The word mole is an old English description which originally referred to dark hairy patches on the skin (congenital naevi) which were likened to the soil burrowing animals. The term mole has since been used much more broadly and as such is not clinically useful. Melanoma can develop in the scattered melanocytes in plain skin or associated with pre-existing pigmented naevi.

Acquired and congenital naevi (moles) Melanocytes and naevus cells do not normally aggregate together to form naevi (moles) until after the first few years of life. Occasionally children are born with pigmented birth marks (congenital naevi).

However, the vast majority of naevi are acquired during the ages of 5 - 20 yrs. During this time new naevi develop and others change, but usually in some proportion to other naevi and overall body growth. The development of new naevi or change in existing ones, especially of single naevi after adolescence is significant and warrants expert assessment.

Factors recognized as increasing the risk of melanoma

• Fair Celtic skin types
  
  
• Skin types which tend to burn rather than tan if exposed to ultraviolet light
  
  
• A history of repeated episodes of sunburn and blistering in childhood and adolescence
  
  
• Other close family members having melanoma
  
  
• Certain types of naevi (moles)

How does melanoma develop

Like cancers in other parts of the body, melanomas are composed of cells which multiply without the normal control of the body's regulating systems. Just as the specific cause of most cancers is not fully understood, it has not yet been possible to completely identify how melanoma develops. However it has been determined that living in climates with high levels of ultraviolet light greatly increases the incidence of melanoma. It appears that the ultraviolet (ionizing radiation) may directly mutate (corrupt) segments of the genetic code located in melanocyte chromosomes and responsible for cell control.

Melanoma results at least in part from the interaction of the accumulated ultraviolet irradiation from the sun and the varying ability of different skin types to resist this damage. Nonetheless melanoma does not always occur in body parts which have received the most solar exposure. It is important to understand that cancers do not develop directly from normal cells but progressively evolve in a series of stages that can frequently be readily identified with expert examination. A number of changes in the skin can be identified as representing changes in the pigment cells which are pre-cancerous.

Examination of the skin

ABCD Guidelines for the early detection of Melanoma

The ABCD guidelines provide a very useful way to monitor your skin and detect the signs of melanoma. It is essential that you seek expert assessment if you notice the following factors:

• A is for ASYMMETRY: One-half of a mole or birthmark does not match the other.
  
  
• B is for BORDER: The edges are irregular, ragged, notched, or blurred.
  
  
• C is for COLOR: The color is not the same all over, but may have differing shades of brown or black, sometimes with patches of red, white, or blue.
  
  
• D is for DIAMETER: The area is larger than 6 millimeters (about the size of a pencil eraser) or is growing larger.

The most important warning sign for skin cancer is a spot on the skin that is changing in size, shape, or color over a period of time. Self-Examination of the skin is an important activity for all those living in Australia and especially those with known risk factors for melanoma.

The Dermascope is an instrument which allows groups of pigment cells within the skin to be examined for changes which signal the development of a melanoma. It is a microscope which is used on living skin. Properly used, this instrument can substantially reduce the need to excise many naevi. Dermoscopy has greatly improved diagnostic accuracy and reduced the need to excise many naevi ( moles).

Some individuals and families with specific forms of dysplastic naevi (unusual moles) can be at particular risk of developing melanoma. These naevi are often greater than 8mm in diameter, have poorly defined margins, and display variegations of pink, tan and brown pigments. These individuals need regular expert monitoring in addition to onging self review.

Dysplastic naevi : These naevi demonstrate dysplastic features.They are larger than 6mm, contain pigment variation and have poorly defined edges.
Multiple dysplastic naevi: This patient has numerous dysplastic naevi and needs close monitoring. Whilst there is the possibility of malignant change within the naevi themselves, the real issue is that the naevi are really indicators of a skin type that is generally at increased risk of developing melanoma.

When are naevi (moles) excised

• If after expert examination there is concern about the possibility of melanoma
  
  
• When the naevus is troublesome due to contact with clothing, jewellery or traumatised by shaving.
  
  
• For cosmetic reasons when the surgeon and patient have considered the spectrum of the potentially resultant scar.

If naevi are stable and do not have any specific clinical features of concern, removing them does not offer any protection against the development of melanoma.