Melanoma

Melanoma is a type of skin cancer that affects melanocytes, the cells that make melanin. Melanin provides pigmentation (colour) to your skin, eyes and hair.

Melanoma happens when melanocytes change and grow out of control. The cell changes usually start in the surface of the skin, either in a mole or in normal skin. If not caught early, it can spread to other parts of your body.

The skin is the outer covering of your body. The skin has two main layers: 

• The outer layer (epidermis) 
• The inner or deeper layer (dermis)

The outer layer has three types of cells: 

• Flat, scaly cells called squamous cells.
• Rounder cells called basal cells, found below the squamous cells. 
• Cells that give skin its colour (melanocytes). These are in between the basal cells. 

Non-melanoma skin cancer affects the squamous cells and basal cells.

Melanoma skin cancer affects the melanocytes.

The deepest layer called the dermis has blood and lymph vessels, hair roots and sweat glands.

Everyone is at some risk for melanoma, but increased risk depends on:

• Exposure to UV light: Exposure to ultraviolet (UV) radiation from the sun’s rays (even on cool or cloudy days) or tanning lamps and sunbeds increases the risk of melanoma.
• Sunbeds: People who have used a sunbed have a 20% increased risk of melanoma. Starting to use them at a young age increases the risk even more. 
• Skin type and eye colouring: People with fair skin with fair or red hair and blue, green or grey eyes are more at risk. 
• Moles: Having a large number of moles or moles which look unusual.
• Age: Risk of developing melanoma increases with age.
• Family history of melanoma or skin cancer: Your risk increases if you have a family member with skin cancer. Remember though melanoma is not infectious and cannot be passed on to others.
• Weakened immune system: For example, after an organ transplant, when taking medicines that suppress your immune system or with illnesses such as HIV/AIDs.
• Genetic skin disorders: Your risk is greater if you have a genetic condition that makes your skin more sensitive to sunlight, such as xeroderma pigmentosum.

Medical content updated from our 'Understanding melanoma' booklet (2023), reviewed by Dr Aoife Lally, Consultant Dermatologist, Katrina Fogarty, Clinical Nurse Specialist Melanoma, Emma O'Riordan, Oncology Liaison Nurse and Sinead Power, Daffodil Centre Nurse.