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Squamous cell carcinoma

What is Squamous cell carcinoma?

Squamous cell carcinoma (SCC) is a common skin cancer which usually develops in areas of excessive sun exposure or other forms of UV radiation (e.g. tanning beds).  They develop from the squamous cells of the skin.  The excessive UV exposure causes a mutation within the cells’ DNA causing unregulated growth of abnormal cells.

SCC usually begins as a precancerous lesion called an actinic keratosis.  It can then progress to SCC-in-situ.  SCC-in-situ is an early lesion which can usually be treated with a cream or liquid nitrogen.  SCC-in-situ is only in the top layer of the skin called the epidermis.  It cannot spread to other areas of the body. 

Invasive SCC has grown beyond the top layer of the skin (from the epidermis to the dermis).  It has the potential to spread to distant tissues (e.g. lymph nodes or organs) especially if untreated.  Fortunately, this is rare for most SCCs.

What does SCC look like?

SCCs can occur anywhere on the body.  They are more common in areas with high levels of sun exposure e.g.  face, lower lip, ear, scalp, backs of hands, upper arms, lower legs. 


There are several ways that they can present, including:

  • A persistent patch of scaly skin

  • An ulcer or sore which does not heal

  • A rough, scaly patch on your lip that may evolve into a persistent ulcer

  • A new ulcer or sore in an old scar

  • A keratotic horn

SCCs are often scaly or develop a horn or a crust.   The squamous cells in the skin are responsible for developing keratin which is involved in creating hair and nails and as a result, the lesions are often scaly or keratin producing.

Am I at risk of developing a SCC?

Factors that increase you risk of SCC are:

  • Excessive sun exposure:  SCC is caused by excessive UV exposure.  . Spending lots of time in the sun — particularly if you don't cover your skin with clothing or sunblock increases your risk of SCC

  • A history of sunburns:  Blistering sunburns as a child or teenager increase your risk of developing SCC as an adult. 

  • Use of tanning beds:  a large dose of harmful UV radiation is received with tanning beds

  • Fair skin:  blue eyes, blond or red hair, tendency to freckle or sunburn easily all increase the risk of developing SCCs

  • Increasing age: SCCs are more common as a person ages

  • A personal history of precancerous skin lesions or any type of skin cancer increases the risk of developing SCC

  • A weak immune system:  People on immunosuppressive drugs for organ transplants or inflammatory medical conditions (e.g. Crohn’s disease) are at increased risk of developing SCCs.  People with weakened immune systems from conditions like leukaemia or lymphoma are also at more risk.

  • Rare genetic disorders: People with xeroderma pigmentosum, which causes an extreme sensitivity to sunlight, have a greatly increased risk of developing skin cancer.

  • People with previous trauma to the skin with resultant large scars e.g. burn scars, chronic wounds or ulcers are at increased the risk of SCC

How can I prevent SCC?

  • Avoid strong sun:  Avoid the sun in the middle of the day (10am -4pm).  Use a UV app to know what level of UV radiation that is currently present.  UVI Apps For Smartphones

  • Wear sunscreen year-round;  Use a broad spectrum sunscreen (UVA, B and C) that is at least SPF 50+.  Re-apply regularly (15 mins before going out in sun and repeat every 2 hours/ reapply after swimming or heavy physical exertion).

  • Wear protective clothing.  Wear a broad-brimmed hat and clothing which covers your arms and legs.  A collared shirt is excellent for the back of your neck.  A good choice of hat for children is:  https://sundayafternoons.co.nz/product-category/kids-hats/   Sunglasses are important to protect your eyes from the sun.

  • Avoid tanning beds

  • Check your skin regularly and see your GP if you develop any concerning lesions.

What to expect at the clinic?

Usually SCC can be diagnosed by examination by Dr Mooney.  Sometimes a biopsy needs to be performed.


The most common way of treating an SCC is with surgery.  This can usually be done under local anaesthetic in the rooms.  This is sometimes done on the day of your first visit.   If more time is needed, a further appointment will be made to have the surgery.


Occasionally, Dr Mooney will recommend you have a general anaesthetic and be treated in the main hospital.

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Possible complications of surgery include:

  • Bleeding

  • Infection

  • Delayed wound healing

  • Scarring

  • Incomplete margins : leaving some of the cancer cells behind

  • Recurrence

  • Further surgery

SCC-in-situ can be treated with liquid nitrogen or efudix cream.

Will my SCC spread ?

SCC of the skin has a low risk of spreading to the lymph nodes or organs.  Some SCCs are considered higher risk and have an increased risk or coming back in the same area or spreading elsewhere.

High risk features for SCC include:

  • Tumour diameter >2cm

  • High risk location: scalp; ear, lip; hands; feet; genitalia

  • High risk features on lab examination of the lesion (histopathology): thickness of tumour >2mm; grade of SCC (poor differentiation); invasion into nerves or blood vessels)

  • Patients with weakened immune systems are more likely to have more aggressive SCCs

 

If you have a high risk SCC, more aggressive treatment will be recommended to reduce the risk of the SCC coming back in the original area or elsewhere on the body.

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