Skin cancer

^{Reviewed September 2023 by Dr Jack Mann, Consultant Dermatologist at Nuffield Health The Holly Hospital and Brentwood Hospital.}

What is skin cancer?

The skin is made up of layers of tissue and different types of cells. The genetic material of cells in the skin can be damaged or changed, producing mutations that affect normal cell growth and division. The abnormal cells then replicate, causing cancer, usually in the form of strange moles, lumps and lesions on the skin.

Skin cancers are divided into two main groups, depending on the cells they develop from:

• Non-melanoma cancers include basal cell carcinomas (the most common form of skin cancer, but very rarely ever spreads) and squamous cell carcinoma (usually grows rapidly and at risk of spreading). These may arise from skin cells called keratinocytes, or other cells in the skin.
• Melanoma is not as common, but causes more deaths in the UK than non-melanoma skin cancers. Melanoma starts in the skin cells called melanocytes (the pigment cells of the skin), which are the cells that form moles. Melanomas typically, therefore, present as unusual or changing moles.

Non-melanoma skin cancer

What is non-melanoma skin cancer?

The vast majority of non-melanoma skin cancers are basal cell carcinomas and squamous cell carcinomas. These both develop in the upper layers of the skin (epidermis). Squamous cell carcinomas arise in keratinocytes. The origin of basal cell carcinomas is a little uncertain, though likely they too arise from keratinocytes or cells in the hair follicles.

There are other forms of non-melanoma skin cancer, but these are even more rare than melanoma. They can be slow growing tumours that resemble basal cell carcinomas (such as atypical fibroxanthoma), though these have the potential to transform into more aggressive malignancies. They also include very aggressive skin cancers such as Merkel Cell carcinoma and angiosarcoma, which can quite readily spread – though these are very rare.

Causes of non-melanoma skin cancer

The exact cause of non-melanoma skin cancer is not clear, but there are factors that increase your risk of developing nonmelanoma skin cancer:

• A family history of skin cancer
• Overexposure to ultraviolet (UV) rays from the sun or sunbeds/sunlamps
• Having very fair skin (easily sunburned)
• Excessive number of moles or freckles
• A weakened or suppressed immune system – from a pre-existing condition (e.g. HIV or CLL) or immunosuppressant medication
• Non-melanoma skin cancer affects slightly more men than women, though the reasons for this are unclear.

Basal cell carcinoma (BCC)

Basal cell carcinoma, also known as a rodent ulcer, occurs in the lowermost layer of your skin. It is the most common type of skin cancer with approximately 75% of skin cancers diagnosed as basal cell carcinoma.* This cancer is very slow growing and usually does not spread to other parts of your body. It usually develops in skin areas exposed to the sun.

Basal cell carcinoma can appear as a small, shiny, coloured, translucent lump. It can also look like a shiny pink or red patch or a brown, black or blue lesion. Over time, the lump or patch may grow, become crusty, itchy, ooze and bleed.

Basal cell carcinoma usually develops in areas of the body that are regularly exposed to the sun, e.g. face, head, neck, torso, arms and legs.

Variants of basal cell carcinoma

Squamous cell carcinoma (SCC)

Squamous cell carcinoma occurs in the top layer of your skin. It is the second most common form of skin cancer, accounting for appoximately 20% of diagnosed skin cancers* This cancer is slow growing, but unlike skin basal cell carcinom,a left untreated, it could spread.

Squamous cell carcinoma can appear as a firm lump with a rough surface, scaly red patches, and usually rapid growth. They are often tender when touched, itchy, bleed easily and can develop into an ulcer that doesn't heal. Squamous cell carcinoma usually develops in areas of the body that are regularly exposed to the sun, e.g. face, head, neck, torso, arms and legs.

Squamous cell carcinomas (SCC) vary in a number of significant ways:

• Intraepidermal/in situ squamous cell carcinoma, also known as Bowen's disease, are technically not cancerous, but precancerous, and can sometimes be treated with creams or liquid nitrogen, rather than surgery.
• carcinomaDifferentiation – the better/more ‘differentiated’ the cancer, the more it resembles the behaviour/appearance of the cells it came from, when looked at under the microscope. Typically the more ‘well’ differentiated, the better, and the more ‘poor’ the differentiation, the more at risk of spreading, though the ability to predict a tumour’s behaviour from its differentiation is a debated subject.
• Invasive characteristics – if a squamous cell carcinoma invades nerves or vessels, it is more likely to spread
• Size – the larger it is when treated, the higher the risk of it coming back or spreading

other rare types of non-melanoma skin cancer

Merkel cell carcinoma

Merkel cell carcinoma is a rare, aggressive type of skin cancer. There remains uncertainty regarding the cell of origin from which these tumours arise. They appear to be associated with advanced age, and it is possible that certain viral infections contribute to its development.

Merkel cell carcinoma can appear in a variety of forms and colours, but usually colourscoloured, pink, red or bluish-red , and can be lumpy or it can form an ulcer. It grows quickly and it can spread to other parts of the body.

Cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma is a rare type of non-Hodgkin lymphoma that affects the skin. Cutaneous T-cell lymphoma appears as patches of red, rash-like patches. These often can be managed with creams or even light therapy, but may require more advanced treatments depending on how they progress.

Kaposi sarcoma

Kaposi's sarcoma is a rare type of cancer that affects the skin and lining of the mouth. It is caused by a virus called human herpesvirus 8, which is also known as Kaposi sarcoma-associated herpesvirus (KSHV).

People with human immunodeficiency virus (HIV) are most at risk of developing Kaposi's sarcoma. However, it can also affect people with weakened immune systems.

Kaposi's sarcoma typically appears as red, brown or purple patches on the skin and can grow into lumps. It can spread to the lymph nodes, lungs and digestive system.

Sebaceous gland cancer

Sebaceous gland carcinoma is a rare type of skin cancer that develops in the sebaceous glands. It most commonly develops on the upper eyelideyelids, but it can develop in other areas of the body. Sebaceous gland carcinoma typically appears as a firm, painless lump.

How is non-melanoma skin cancer treated?

Surgery is the main treatment option for skin cancers. Other treatment options for non-melanoma skin cancer include:

• Cryotherapy, where skin cells are frozen in order to destroy the cancer cells. This is usually reserved for precancerous lesions
• Radiotherapy, where high-energy rays are used to destroy the cancer cells
• Topical creams such as 5-fluorouracil or Imiquimod
• Photodynamic therapy (PDT), where a special light activates a cream which has been applied to the affected area of skin, killing the abnormal cells in the skin, but this is more typically used to treat thinner or precancerous lesions.

Depending on the type of non-melanoma skin cancer you have, your consultant or oncologist will create a treatment plan to suit your individual needs.

Melanoma skin cancer

What is melanoma skin cancer?

Melanoma skin cancer refers to the types of skin cancers that develops in the skin cells called melanocytes (the skin cells that produce melanin and, when they form benign tumours, they form normal moles). Melanoma skin cancer typically presents as a change to an existing mole or a new pigmented growth on the skin.

Types of melonama:

• Superficial spreading melanoma
• Nodular melanoma
• Lentigo maligna melanoma
• Amelanotic melanoma
• Acral lentiginous melanoma

Causes of melanoma skin cancer

The exact cause of melanoma skin cancer is not clear, but there are factors that increase your risk of developing melanoma skin cancer:

• A family history of melanoma
• Overexposure to ultraviolet (UV) rays from the sun or sunbeds/sunlamps
• Excessive number of moles or freckles
• Having very fair skin (easily sunburned)
• Large, pigmented birthmarks
• A weakened or suppressed immune system – from a pre-existing condition (e.g. HIV) or immunosuppressant medication

Types of melanoma skin cancer

Superficial spreading melanoma

Superficial spreading melanoma is the most common type of melanoma - approximately 70% of people diagnosed with melanoma have superficial spreading melanoma.* It typically starts growing outwards rather than downward into the skin.

Superficial spreading melanoma tends to appear flat or slightly raised with an irregular shape. It can be a range of different colours including brown, black, red/pink, blue or white.

Superficial spreading melanoma can appear anywhere on the body. However, it is most likely to appear on the legs for women, and on the torso for men.

Nodular melanoma

Nodular melanoma is the second most common type of melanoma, with 15% of people diagnosed with melanoma having nodular melanoma*. It can grow quickly over several weeks or months.

Nodular melanoma appears as a lump or bump on the skin. It is often black or brown but can appear red or have no colour.

Nodular melanomas can appear anywhere on the body. However, it is most likely to appear on the head, neck and torso.

Lentigo maligna melanoma

Lentigo maligna melanoma also called Hutchinson’s melanotic freckle, is a rare type of melanoma. It is very slow growing and usually develops in areas of the body that are regularly exposed to the sun - the face, neck, arms and torso.

At first, lentigo maligna melanomas often resemble a freckle. Over time it will change shape and colour and become more distinctive. Lentigo maligna melanomas are typically flat with an irregular shape. It can be a range of different colours including brown, dark brown, black, red or pink.

Acral lentiginous melanoma

Acral lentiginous melanoma (ALM) is a rare type of melanoma. Approximately 5% of people diagnosed with melanoma have acral lentiginous melanoma. It is the most common type of melanoma found in people of colour.

Acral lentiginous melanoma tends to be found on hands and feet - palms, soles of the feet, fingernails and toenails – areas where the skin is less pigmented, and therefore less resistant to the harmful effects of ultraviolet radiation.

Acral lentiginous melanomas can be grey, red, brown or black with an irregular shape. It may be flat and smooth, but as it develops it can become rough and thicker.

Amelanotic melanoma

Amelanotic melanoma is a rare type of melanoma. Around Up to 8% of people diagnosed with melanoma have amelanotic melanoma.*

Amelanotic melanoma have no colour, but may be pink, red or skin coloured, making it difficult to diagnose. It will have an irregular shape and may have light brown, brown or grey edges.

How is melanoma skin cancer diagnosed?

Your consultant will advise you on which tests are relevant to your individual symptoms. On physical examination, a melanoma is suspected, then a skin biopsy is necessary to confirm the diagnosis. Once a melanoma is removed, in the vast majority of cases this means the cancer has been treated fully, but sometimes other investigations are needed, such as:

• A Sentinel Lymph Node biopsy, a test to determine whether microscopic amounts of melanoma might have spread to the lymph nodes
• A CT scan, which shows a 3D image of the area being looked at
• An MRI scan, a procedure that uses radio waves and a computer to make a series of detailed pictures of areas inside the body
• A PET scan – Positron Emission Tomography
• Blood tests

Stages of melanoma skin cancer

Health professionals use a staging system to describe how far melanoma has grown into the skin (the thickness) and whether it has spread. The type of treatment you receive will depend on what stage the melanoma has reached.

The stages of melanoma can be described as:

• Stage 0 – the lesion is only precancerous, ‘in situ’ melanoma, and technically not cancer, but at risk of transforming into melanoma.
• Stage 1 and Stage 2 relate to the thickness of the melanoma and other features, such as whether it is ulcerated or not.
• Stage 3 – the melanoma has spread into nearby lymph nodes or lymphatic channels
• Stage 4 – the melanoma cells have spread to other areas of the body, such as the lungs, brain or other parts of the skin

Each stage consists of several subtle, technical stages, which can best be described to you by your doctor.

How is melanoma skin cancer treated?

Depending on the type of melanoma you have and the stage of the cancer, your consultant will create a treatment plan to suit your individual. Treatment options include:

• Surgery to remove the cancer.
• Surgery to remove the skin around where the melanoma was, to reduce the chance of it coming back.
• Surgery to remove nearby lymph nodes, depending on the stage of the cancer.
• Radiotherapy, where high-energy rays are used to destroy the cancer cells.
• Chemotherapy, where chemical agents destroy the cancer cells, preventing them from spreading to different areas.
• Immunotherapy

Sources:
*Cancer Research UK https://www.cancerresearchuk.org/about-cancer/melanoma/stages-types/types Variants of basal cell carcinoma