Melanoma is a malignant cancer that starts from the pigment cells (melanocytes) of the skin. These cells are the cause of freckles and moles on the skin and produce the brown colour of a suntan.

Melanoma can occur anywhere on the skin, even on the soles of the feet.  Melanocytes in the eye, nervous system and mucous membranes (eg lining of the mouth and nasal passages) can also become cancerous. These types of melanoma are rare.

Melanoma grows quickly. If it is not treated, it may spread to the lower layer of skin, where cancer cells can escape and be carried to other parts of the body in blood or lymph vessels.

In particular, it is of great importance to Australians for two main reasons:

• Australia has the highest incidence of melanoma in the world
• It is often 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

The skin has many important jobs. It protects us from injury, cools us when we get hot and prevents us from becoming dehydrated.  The skin has two main layers: the epidermis and the dermis.

The epidermis is the top or outer layer. It contains two main types of cells: squamous cells and melanocytes. The melanocytes produce melanin, the substanced that gives skin its colour. When skin is exposed to sunlight, the melanocytes produce more melanin and the skin becomes tanned.

The dermis is underneath the epidermis. It contains the roots of hairs, glands that make sweat and oil, blood and lymph vessels and nerves.

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 sunlight (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 moles: junctional, dermal, compound and dysplastic naevi. 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 more broadly and as such is not clinically used.

It is important to note that Melanoma can develop in the scattered melanocytes in plain skin or associated with pre-existing pigmented naevi (moles).

MOLES & MELANOMA

Acquired and congenital naevi (moles)

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

However, most naevi (moles) are acquired from the age of 5 up to 20 years. 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 (moles) or change in existing ones, especially of single naevi after adolescence is significant and we recommend medical advice be sought.

Dysplastic naevi : These naevi (moles) demonstrate abnormal features. They are larger than 6mm, contain pigment variation and have poorly defined edges.

Multiple dysplastic naevi: This patient has numerous dysplastic naevi (moles) 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) removed?

• If after expert examination there is concern about the possibility of melanoma
• When the naevus (mole) is troublesome due to contact with clothing, jewellery or traumatised by shaving.
• For cosmetic reasons - the surgeon and patient will need to consider any potential scaring.

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

TYPES OF MELANOMA

1. Superficial spreading melanoma: grows initially in the top layer of the skin (the epidermis). This type becomes dangerous when it invades downward into the lower layer of the skin (the dermis).
    
2. Nodular melanoma: often very dark brownish black or black in colour but can be pink or red. It forms a raised lump on the surface of the skin as it invades deeper into the skin.
    
3. Acral lentiginous melanoma: most commonly found on the palms of the hands and soles of the feet or under the nails. This type is more common in people with darker skin.
    
4. Lentigo maligna melanoma: appears in areas of skin that get a lot of sun exposure, such as the face and upper body. It may grow slowly and superficially over many years, later forming lumps as it grows deeper into the skin.

Melanoma Images