Skin cancer

What is skin cancer?

Skin cancers are malignant tumours in which there is an uncontrolled proliferation of any one of the many skin cell types, whereas the normal process of regeneration of skin involves replication of the cells in a controlled fashion. Each subtype of skin cancer has unique characteristics.

The most common forms of skin cancer are:

• Basal cell carcinoma (BCC)
• Squamous cell carcinoma (SCC), including keratoacanthoma
• Melanoma.

The term non-melanoma skin cancer refers to all types of skin cancer apart from melanoma. BCC and SCC are also called keratinocyte cancer.

Basal cell carcinoma

Squamous cell carcinoma

Melanoma

Early, superficial skin cancers include:

• Superficial basal cell carcinoma
• Intraepidermal squamous cell carcinoma (Bowen disease, in-situ squamous cell carcinoma) and actinic keratoses
• Melanoma in situ.

Many different types of less common skin cancer are listed in the related information section at the bottom of this page.

Who gets skin cancer? 

Skin cancer most commonly affects older adults, but it can also affect younger adults, and rarely, children.

• Skin cancer tends to affect individuals with fair skin (Fitzpatrick skin phototype I, II and III), although people with darker skin can also develop skin cancer.
• People who have had skin cancer have an increased risk of developing other skin cancers.
• A family history of skin cancer also increases risk.  
• Certain genes such as melanocortin-1 receptor have been identified as carrying an increased risk of skin cancer.

What causes skin cancer?

The common forms of skin cancer listed above are related to exposure to ultraviolet radiation (from sunlight or tanning beds) and the effects of ageing. Other risks include:

• Smoking (especially for SCC)
• Human papillomavirus infection (genital warts), particularly for mucosal sites such as oral mucosa, lips, and genitals 
• Drug-induced immune suppression, for example in patients who have received an organ transplant and are on azathioprine and ciclosporin
• Other medicines such as hydrochlorothiazide
• Human immunodeficiency virus infection (HIV)
• Exposure to ionising radiation
• Exposure to certain chemicals, such as arsenic and coal tar
• Longstanding skin diseases such as lichen sclerosus, lupus erythematosus, linear porokeratosis or cutaneous tuberculosis
• A longstanding wound or scar, for example, from a thermal burn (Marjolin ulcer).

Some skin cancers are due to genetic conditions, such as:

• Albinism
• Basal cell naevus syndrome (Gorlin syndrome)
• Bazex–Dupré–Christol syndrome
• Bloom syndrome
• Brooke-Spiegler syndrome
• Cowden disease
• Dyskeratosis congenita
• Epidermolysis bullosa
• Epidermodysplasia verruciformis
• Familial atypical multiple mole and melanoma syndrome (FAMMM) 
• Premature ageing syndromes (progeria)
• Rothmund-Thomson syndrome
• Muir-Torré syndrome
• Xeroderma pigmentosum.

What are the clinical features of skin cancer?

Skin cancers generally appear as a progressive lump or nodule, an ulcer, or a changing lesion.  

What are the complications of skin cancer?

Skin cancer can usually be treated and cured before complications occur. Signs of advanced, aggressive, or neglected skin cancer may include:

• Ulceration
• Bleeding
• Local invasion and destruction of adjacent tissues and structures
• Distant spread of a tumour to lymph glands and other organs such as liver and brain (metastasis). 

How is skin cancer diagnosed?

Skin cancers are generally diagnosed clinically by a dermatologist or family doctor, when learning of an enlarging, crusting, or bleeding lesion.  The lesion will be inspected carefully, and ideally, a full skin examination will also be conducted.

• Dermoscopy (using a special magnifying light) may be used to confirm the diagnosis, to detect early skin cancers, and to exclude benign lesions.
• A partial skin biopsy may be taken in cases of suspected non-melanoma skin cancer to confirm the diagnosis or determine a subtype which may influence treatment.
• Complete excision is usually undertaken to make a diagnosis if melanoma is suspected, as a partial biopsy can be misleading in melanocytic tumours.
• The diagnosis is confirmed in the laboratory by a histopathologist. It can take a few days for the report to be issued, or longer if special tests are required.
• Genetic testing for melanoma and blood-based melanoma detection may be available in some centres.
• Further investigations may be required if there is a suspicion spread has occurred.

What is the differential diagnosis of skin cancer?

The differential diagnosis of skin cancer depends on the specific lesion.  

What is the treatment for skin cancer?

Early treatment of skin cancer usually cures it. The majority of skin cancers are treated surgically, using a local anaesthetic to numb the skin. Surgical techniques include:

• Excision biopsy
• Wide local excision
• Mohs micrographic surgery.

Treatment options for superficial skin cancers include:

• Minor surgery including curettage and diathermy/cautery and electrosurgery
• Cryotherapy
• Topical therapy such as fluorouracil cream, imiquimod cream or ingenol mebutate gel 
• Photodynamic therapy (photosensitising cream plus light)
• Radiotherapy (x-ray treatment)
• Lasers.

Treatment for advanced or metastatic basal cell carcinoma may include targeted therapies vismodegib and sonidegib.

Treatment for advanced and metastatic melanoma may include:

• Systemic immunotherapy using ipilimumab or checkpoint inhibitors pembrolizumab or nivolumab
• Topical and intralesional immunotherapy for melanoma metastases
• Targeted therapy against BRAF mutations using vemurafenib or dabrafenib or MEK inhibition with trametinib
• Combination medications, such as cometinib.

Patients with skin cancer may be at increased risk of developing other skin cancers. They may be advised to:

• Practice careful sun protection, including the regular application of sunscreens
• Learn and practice self-skin examination
• Have regular skin checks
• Photographic surveillance
• Undergo digital dermoscopic surveillance (mole mapping), especially if they have many moles or atypical moles 
• Seek medical attention if they notice any changing or enlarging skin lesions
• Take nicotinamide (vitamin B3) or acitretin (off-label) to reduce the numbers of squamous cell carcinomas.  

These treatments can lead to adverse effects. See:

• Cutaneous adverse effects of checkpoint inhibitors
• Cutaneous adverse effects of antimelanoma therapies.

What is the outcome of skin cancer?

Most skin cancer can be completely cured with early treatment. Advanced skin cancers are more difficult to treat and can lead to death.