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Expert Opinion

Understanding Types of Skin Cancer and Treatments Available

By Consultant Dermatologist, Bav Shergill


Current predictions of the incidence of skin cancer suggest that even if everybody takes sensible precautions against excessive sun-exposure, the UK will experience at least a 300% rise in cases over the next 20 years (Diffy BL, 2004.  British Journal of Dermatology.  151;4 868-872).

 The two major factors that contribute to this skin cancer epidemic are our sun-seeking behaviour and our longer life spans.  We all love the sun.  It makes us feel good, lifts our mood and allows us to do all the outdoor activities that we enjoy.  However, sunlight carries ultraviolet (UV) radiation which can damage our DNA.  If the DNA is damaged in the cells in our skin, they may mutate into cancer cells.  

Preventing Skin Cancer

Prevention is far better than a cure.  Taking care to protect our skins from sun damage reduces our cancer risk and makes us look younger for longer.

  • Avoid sun exposure between 11.00am and 3.00pm.
  • Cover up - wear a hat to shade your face from the sun, sunglasses and a t-shirt.  Take extra care if you work outdoors
  • Cover up children -. Childhood sunburn is strongly associated with later skin cancer. UV protection sun-suits are good for wearing on the beach.
  • Use a good sun cream.  I recommend using reflecting sunscreens with a factor of SPF50 and above.  The SPF refers to how much the cream will delay sunburn.  For example, if you burn within a minute of sun-exposure, an SPF50 cream will permit you 50 minutes of exposure until you burn.  It just delays the inevitable.  Ensure that you follow the instructions on the bottle carefully, reapplying when necessary.

However, sun avoidance is best.

 Actinic Keratosis (AK)

These are very common pre-cancerous lesions that are found on sun-exposed skin.  Patients can start to develop them as early as 30, although they are more common in the 50+ age group.  They look like dry, crusty patches of skin measuring from as little as 3mm in diameter.  They are most commonly found on the backs of the hands, the head and the neck.  The risk of them progressing to skin cancer varies between 1 in 1,000 to 1 in 10,000 per year.  It is good practice to treat them.

 Treatment of AKs:

Cryotherapy involves spraying liquid nitrogen onto the lesion for 5-10 seconds.  This causes a very localised frostbite.  Over the next 7-10 days, the skin becomes red, starts to scab and eventually falls off.  The resulting scar can be very pale.

Efudix is a chemotherapy cream that is applied to the affected area one to two times a day for 3-4 weeks.  The skin goes very red and can weep and scab.  After the treatment is completed, the skin heals over a 2-3 week period and looks normal again.  It is an excellent treatment, but patients are often reluctant to use it due to the long period of redness.

Picato is derived from plant sap and only requires 2-3 days to have an effect on AKs.  It causes a lot of redness and peeling during the first 7 days following treatment but the skin looks better after 2 weeks.

Photodynamic therapy is as successful as Efudix in treating AKs.  It has a shorter healing period (1-2 weeks typically) and involves one or two treatment sessions.  (please see my website www.glowdermatology.com for further details of this procedure)

Surgery can be useful for AKs that haven’t responded to the other treatments.  They can be cut out or scraped off.

My usual approach is to use Efudix and Photodynamic therapy to treat large areas of sun-damaged skin rather than just the AK alone.  The benefits to this approach are that any premalignant cell that can’t be seen yet will be destroyed and the skin will appear rejuvenated after the treatment, leaving no scars.

Squamous Cell Carcinoma (SCC)

 This tumour falls between melanoma and basal cell carcinoma in terms of incidence and aggression.  There are approximately 20,000 cases of SCC a year, occurring mainly in the elderly and those who have received transplants.

They usually appear as skin-coloured lumps or crusts that grow over 6 months, often developing a crater or a bloody ulcer in the centre.  They are usually located on sites of chronic sun-exposure such as the head, hands and lower legs.

Any suspicious lumps should be sampled by taking a biopsy from the skin and sending them to a pathologist for detailed examination.  The pathologist will indicate which sub-type of SCC is present.

 SCC Sub-types:

Well differentiated SCCs are the commonest type and they very rarely spread internally to other organs.  They are often dome-shape with a central crust and may be tender.  They are best removed surgically.

 Moderately differentiated SCC and Poorly differentiated SCC are more aggressive.  There is a higher risk that they will spread internally (up to 30% chance in some).  They should be surgically removed.

 Intraepithelial SCC (also known as Bowen’s disease) is only found in the epidermis (outermost layer of the skin) and does not invade deeper into the body.  However if they are left alone, after a period of several years or even longer they may start to invade like a well-differentiated SCC.  They can be treated with Efudix, photodynamic therapy, cryotherapy or surgery.

If an SCC has spread internally, it usually spreads to the lymph nodes adjacent to the original tumour site.  These lymph nodes are situated in the neck, armpits and groin and can be detected by a clinical examination.  It may then be necessary to have a Computerised Tomography (CT) scan to look for tumour spread elsewhere.  If this is the case, then the SCC can be treated with surgery and/or chemotherapy.

 Melanoma

This is the most aggressive skin cancer and has an annual incidence of approximately 13,000 cases in Britain.  The incidence is increasing by 4-5% every year.  The majority of melanomas are found and removed at an early stage in their development and cure rates in this situation are up to 99%. However, if left untreated, melanoma can spread throughout the body and is much more difficult to treat.

Melanoma subtypes:

 Superficial Spreading Malignant Melanoma is the commonest subtype of melanoma, making up almost 70% of cases.  It is often found on the head, neck and torso.  The appearance is often of an irregular shaped, brown-black mark that is usually greater than 6mm in diameter.  Occasionally it can be ulcerated and bleed.  It normally grows for between 6-18 months before the patient becomes aware of it.

Nodular Malignant Melanoma is an aggressive subtype of melanoma, making up approximately 20% of all cases.  It is characterised by a rapidly growing lump that is usually dark brown or black in colour.  It can develop over a couple of months, starting off as 1-2mm and then usually progressing to between 5-10mm before being discovered by the patient.  Occasionally it can become ulcerated and bleed.

Lentigo Maligna Melanoma is often seen at sites of chronic sun exposure in the elderly population.  It is characterised by an early stage known as Lentigo Maligna, where the melanoma cells are confined to the top layer of the skin (epidermis).  It can appear as a brown flat mark, usually over 1cm in diameter.  Removal at this stage has an excellent prognosis.  If left, it can become an invasive melanoma which carries a poor prognosis.

 Acral Lentiginous Malignant Melanoma is rare and often seen in patients of African and Asian origin.  It appears as a flat mark composed of different shades of brown and black, located on palms, soles and underneath fingernails.  Bob Marley died of this cancer.  Careful examination and good clinical judgement is required to make the diagnosis.  These tumours are normally picked up quite late and therefore have a poor prognosis.

Amelanotic Malignant Melanoma is a rare group of melanomas that are not black or brown in appearance.  They often appear pink and in some cases can be mistaken for eczema.  Careful examination and good clinical judgement is required to make the diagnosis.  These tumours are normally picked up quite late and therefore have a poor prognosis.

Treatment and Staging

All melanomas are surgically removed to allow for treatment and diagnosis.  Initially an excision biopsy is performed, removing the suspected tumour with an extra 2mm margin around the edge.  This is sent to a pathologist for careful examination.  They check whether the tumour has been fully removed and also comment on the thickness of the tumour.  This is known as the Breslow Thickness and is one of the best ways of assessing the severity of the tumour.

Depth

Survival after 5 years

Less than 1mm

90 - 99%

1-2mm

75 - 90%

2-4mm

65 - 78%

Greater than 4mm

45 - 65%

 

The majority of patients have tumours less than 1mm, which require further surgical removal with either a 5mm or 10mm margin.  This is usually all the treatment that they will ever need.  The thicker tumours will be removed with a larger margin, of up to 20mm.

It is rare that the tumour has already spread to other organs, but if this is the case then the survival rates are much lower.  If clinical observations suggest that the tumour may have spread from the original site, a whole body scan is undertaken.  The positron emission tomography (PET) and computerised tomography (CT) combined scan is the most effective for picking up spread of melanoma.

 If the tumour has already spread internally then further surgery and/or chemotherapy will be offered.  Historically, response rates have been low but there are new therapies such as EGFR inhibitor, MEK inhibitors and PD1 inhibitors that are showing great promise in prolonging disease-free survival.

 Basal Cell Carcinoma (BCC)

This is the commonest skin cancer in Britain with an estimated incidence of 200,000 cases a year.  Fortunately, it is rarely lethal.  It causes damage by spreading throughout the skin, muscle, eyes, ears and other structures.  The rate of spread is thought to be only 1mm every 3 months, but as the tumours can be very subtle in appearance they are usually present for at least a year before diagnosis.

The main symptom is one of bleeding and scabbing of the affected skin with a failure to heal, which is often noticed when washing.  Patients can often be surprised when told that they need an operation as the BCC may seem to have disappeared.  It hasn’t, it is just not bleeding as much as before and if left, it will bleed and scab further, as well as get bigger.

BCC Subtypes:

Superficial BCCs are very thin tumours that look like red patches of eczema.  They are often found on the head, neck, back and chest.  They can be treated with chemotherapy creams, liquid nitrogen spray, photodynamic therapy or surgery.

Nodular BCCs are often dome shaped and skin coloured with fine vessels on them.  These tumours can ulcerate giving a crater-like appearance.  They are best treated with surgery.

 Morphoeic BCCs or Infiltrative BCCsare the most aggressive subtype of BCC.  They are also very subtle in their clinical appearance and may appear as waxy, pale patches on the skin.  They are usually located on the head and neck, which can cause problems as their roots can extend very far into local and deeper tissues. Failure to fully remove these tumours can lead to loss of vision or destruction of the nose, ear and nerves. The most successful treatment for these tumours is Mohs surgery.

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