What is skin cancer?

Cancer occurs when cells become abnormal, grow uncontrollably and have the potential to spread to other parts of the body. These cells build up to form a mass (or lump). 

Skin cancers occur, when cells are damaged by ultraviolet (UV) light from the sun and use of solariums. Light from the sun has some radiation, it is the radiation that is harmful. When found early, most skin cancers can be managed with local treatment that does not have long-term side-effects.

Skin cancer can be found on any part of the body. It is the most common cancer diagnosed in Australia. These cancers are either: non-melanoma skin cancers (NMSC) or melanoma. The treatment for these two groups is different, that makes it important to know the type of skin cancer.

NMSC are far more common than melanoma and are typically found on the head and neck in middle aged and older people  due to long term sun exposure. People can also get skin cancers on their arms, legs and trunk.

There are two common types of NMSC:

  • Basal cell carcinoma (BCC): is a tumour of the basal layer of the skin. BCCs are mostly a local problem. They usually grow slowly but can become very big and destroy tissue close to the tumour (locally), but rarely spread to other parts of the body (metastasise).

  • Squamous cell carcinoma (SCC): starts in the top layer of skin cells. It often starts as hard scaly skin (actinic keratosis) and abnormal cells (dysplasia) and SCC in situ (sometimes referred to as Bowen’s disease). A small number can travel to (metastasise) nearby lymph nodes, or be locally aggressive, and require more complex treatment.

Melanomas are less common than NMSC and can occur in younger people often as a result of previous sunburns. In Australia, melanoma is the fourth most common cancer. Sunburn causes 95% of melanomas and it is very treatable when found in its early stages

Melanoma is a cancer of melanocytes, the pigment cell in the basal layer of the skin. Like other skin cancers, melanoma is only invasive when it breaks through the bottom membrane of the skin and invades deeper tissues. Melanoma is more likely to come back (recur) and to metastasise if it has invaded the deep tissue The chance that a melanoma will spread is related to how thick or deep it has grown into the deep tissue, sores (ulceration) and other microscopic features. Melanoma can grow anywhere on the body  including sun exposed skin, soles of the feet, under finger and toe nails and in the eye

Merkel cell carcinoma (MCC) (cancer of neuroendocrine cells in the skin) is a rare skin cancer that may spread to the lymph nodes. It is most commonly found in older people. Sun exposed areas, including the head and neck, arms and legs are the areas usually affected. MCC is treated most commonly with radiation therapy, although surgery may be an option. 

What causes skin cancer?

In Australia, sun exposure is a major risk factor for skin cancer. UV exposure in childhood and built up over a lifetime increases the risk of skin cancer, especially NMSC.
Other factors that may increase the risk of skin cancer are: 

previous skin cancer 
fair complexion and inability to tan 
poor immune system
family history of melanoma
having moles on the skin
genetic predisposition, e.g. basal cell naevus syndrome, dysplatic naevus syndrome, xeroderma pigmentosum