SKIN CANCERS & CONDITIONS
Squamous cell carcinoma
SCC is a common skin cancer, especially in older people. It’s usually easily treated, but sometimes spreads.
- Can develop from solar keratoses
- May appear as a firm crusty lump
- Several hundred Australians die of SCC yearly
Squamous cell carcinoma, also known as SCC, usually grows on sun-exposed parts of the body without causing serious medical problems, but it can spread in some cases. If diagnosed early, SCC is easily treated, but a small percentage of cases can be fatal.
99% of squamous cell carcinomas are caused by ultraviolet (UV) radiation from sun exposure.1 UV radiation damages DNA in cells, so that they no longer grow correctly and skin cancer can develop.2 Squamous cell carcinoma is caused by cumulative long-term sun exposure over many decades3, including in adulthood and later life, meaning that people who work outside are at higher risk.4
In some cases, the human papilloma virus (HPV), which causes warts and cervical cancer, appears to act together with sun exposure to lead to the development of SCC.5
Statistics for squamous cell carcinoma show that the number of new cases in Australia doubled between 1985 and 2002. In 2002, approximately 80,000 cases of SCC were diagnosed.4
Squamous cell carcinoma is more common with increasing age, with the vast majority occurring in people aged 55 and above.3 Males are approximately one and a half times more likely to develop SCC than females.1 Each year in Australia, over 600 people die from SCC.6
“Each year in Australia, over 600 people die from SCC.”
Risk factors
Major risk factors for developing squamous cell carcinoma are:
- Previous squamous cell carcinoma or basal cell carcinoma: Up to 60% of people with one of these non-melanoma skin cancers develop another in the next three years.7
- Immunosuppression (i.e. a poor immune system). This is common in people taking certain medications, e.g. transplant recipients, people on chemotherapy or long-term steroids, or some medications for arthritis or inflammatory bowel disease. Medical conditions causing immunosuppression (e.g. AIDS) can also increase the risk of developing SCC or other skin cancers.
- Exposure to arsenic8.
- Fair complexion, a tendency to burn rather than tan, the presence of freckles, light eye colour, light or red hair colour.
- Age over 40 years.
- Male.
- Presence of multiple solar keratoses.
- High levels of ultraviolet exposure such as outdoor workers.
- Solarium use: The risk of SCC is twice as high in people who have used a solarium before the age of 25, compared with people who have never used a solarium.4
- Smoking, in particular for SCC of the lip. Current smokers are up to three times more likely to develop SCC than non-smokers.9
Outdoor workers have up to 5 times higher risk compared with people who have only worked indoors.4
What does squamous cell carcinoma look like?
In men, squamous cell carcinoma occurs most commonly on the head and neck. In women, the arms are affected most, followed by the head and neck.10 Most squamous cell carcinomas grow from pre-existing solar keratoses (although the chance of any given solar keratosis turning into a squamous cell carcinoma is very low).4
Symptoms of SCC may include:
- Thickened red, scaly spot.
- Rapidly growing lump, with a crust on its surface.
- A sore which does not heal after several weeks or months.
- In some cases, SCC may be tender to touch.
MBBS, MA (Virtual Comm), Grad Cert Hlth Info, Grad Dip Comp Inf Sci
Squamous cell carcinoma: a crusted surface on a red patch of skin
Squamous cell carcinoma: a crusted surface on a red lump
SCC can occasionally be difficult to diagnose. It usually appears in areas of sun damage and solar keratoses, and is easily mistaken for an overgrown solar keratosis. In cases where the diagnosis is unclear, a punch or shave biopsy may be required to establish the diagnosis and suitable treatment.6
Progression
If untreated, squamous cell carcinoma will usually enlarge gradually, leading to bleeding and ulceration. As it grows, it may become more tender to touch.10
Large SCCs sometimes grow into the tissue surrounding nerves in the skin. This is known as perineural spread, and means that there is a higher risk of the SCC:
- Being difficult to cure.
- Returning after treatment.
- Spreading to other organs. This type of spread occurs in 4 per cent of SCC cases.12
Different types of SCC progress in other ways.
Superficial squamous cell carcinoma (also called Bowen’s disease, intraepithelial carcinoma or squamous cell carcinoma in situ) affects the top layer of skin and appears as a red rough/scaly patch rather than a lump with a crust. It usually grows very slowly – the patient may have difficulty noticing changes. Bowen’s disease rarely progresses to invasive squamous cell carcinoma and is usually easy to treat.
Keratoacanthoma is a rapidly-growing form of squamous cell carcinoma which can appear over a period of weeks. It is unusual for keratoacanthoma to become invasive and in many instances it disappears by itself. This doesn’t always happen, and it’s not possible to predict when it will, so it is usually treated by surgical removal.
Treatment of squamous cell carcinoma
Squamous cell carcinoma is usually treated effectively with surgical removal (also called excision). The entire cancer must be removed with a margin of at least 2mm (but sometimes more) of normal skin around its edges.5
Bowen’s disease affects only the upper part of the skin and can be treated from the surface using cryotherapy (freezing), a chemotherapy cream or photodynamic therapy. Each of the treatment options has advantages and disadvantages and should be discussed with a doctor.
Follow-up: what happens next?
In most cases, once a squamous cell carcinoma is excised, no further treatment is required.
Specialist referral
In some circumstances, your doctor may refer you to another doctor or health service for further treatment or assessment. For example:
- A plastic surgeon can perform a wide excision of a squamous cell carcinoma to achieve a good cosmetic outcome or preserve function of the affected area.
- A public hospital dermatology unit can offer a team approach where surgeons, dermatologists, oncologists skin pathologists and other specialties are involved in your care. This may be required if you have a high-risk squamous cell carcinoma with signs of perineural spread or other microscopic warning signs.
Reducing the risk
Regular skin checks will help detect evidence of the cancer returning and allow detection of new skin cancers.
For most people, 12-monthy skin checks are recommended. If there’s a history of multiple or high-risk skin cancers, we may recommend 6-monthly skin checks.
Solar keratoses sometimes develop into squamous cell carcinoma. Treating them may reduce the risk of SCC. Treatment options include cryotherapy (freezing) of individual solar keratoses and prescription creams, photodynamic therapy or fractional laser treatment of larger areas.
To detect skin cancers that appear between appointments, check your own skin every 2-3 months (or more if you wish). Report any new, changing or “ugly duckling” spots that look different from your other spots and lumps.
Vitamin B3 tablets (2 × 500mg tablets per day) could reduce your risk of future skin cancers and solar keratoses. If you are considering taking vitamin B3, discuss potential benefits and side effects with your doctor.
Prevention of squamous cell carcinoma
Primary prevention: for people who have never had a squamous cell carcinoma
Because the majority of squamous cell carcinomas are caused by ultraviolet radiation, avoiding excessive sun exposure is the most important measure for prevention. The risk of squamous cell carcinoma is increased by sun exposure in later life, so reduction of sun exposure at any age can help reduce the risk.
When the ultraviolet index is greater than 3, recommended methods for reducing sun exposure include:
- Wearing long sleeves and pants, hats and sunglasses.
- Using broad spectrum sunscreen with SPF of 30 or greater.
- Seeking shaded locations.
Other measures to reduce SCC risk include:
- Avoiding or giving up smoking.
- Avoiding solarium use.
There is some evidence that a diet rich in leafy green vegetables can reduce the risk of SCC11, and one study has found lower rates of SCC in people who regularly take non-steroidal anti-inflammatory drugs such as aspirin.13
Secondary prevention: to prevent future squamous cell carcinomas in people who have previously had an SCC
Regular skin checks can prevent squamous cell carcinoma through the detection and treatment of pre-cancerous solar keratoses. When squamous cell carcinoma is detected at a skin cancer check-up, it is more likely to be early and therefore easier to treat and less likely to result in serious medical consequences or death. Daily use of sunscreen significantly reduces the risk of squamous cell carcinoma in people who have already had one.14
“Daily use of sunscreen significantly reduces the risk of squamous cell carcinoma in people who have already had one.”
Vitamin B3 (taken in the form of nicotinamide 1000mg daily) reduces the development of future squamous and basal cell carcinomas by 23 per cent.15 Vitamin B3 must be taken with caution since there new evidence that suggests some people taking vitamin B3 may have a higher risk of cardiovascular conditions such as heart attack and stroke.16
There are case studies of HPV vaccine being successfully used to treat and prevent the recurrence of SCC in patients unsuitable for surgical treatment.17
References
- Cancer Council Australia 2016. Sunsmart national position statement: sun exposure and vitamin D – risks and benefits, in Cancer Council position statements.
- Australian Institute of Health and Welfare 2016. Skin cancer in Australia.
- Leiter U, Garbe C, 2008. Epidemiology of melanoma and nonmelanoma skin cancer: the role of sunlight. Advances in Experimental Medicine and Biology, vol. 624, pp. 89–103
- Cancer Council 2020. Risk factors/epidemiology, in Skin cancer statistics and issues.
- Cancer Council Australia 2021. Optimal care pathway for people with keratinocyte cancer (basal cell carcinoma or squamous cell carcinoma), second edition, in Optimal cancer care pathways.
- Cancer Council Australia 2016. Skin cancer incidence and mortality, in Skin cancer statistics and issues.
- Royal Australian College of General Practitioners 2018. Skin cancer, in “Red Book” guidelines for preventive activities in general practice.
- Centeno JA, Mullick FG, Martinez L, et al 2002. Pathology related to chronic arsenic exposure. Environmental Health Perspectives. 2002;110 Suppl 5:883–886.
- Whiteman D, Green A, Olsen C 2019. Epidemiology of cutaneous squamous cell carcinoma, in Clinical practice guidelines for keratinocyte cancer.
- Rawlin M, Reid C et al 2019. Clinical features of cutaneous squamous cell carcinoma and related keratinocyte tumours, in Clinical practice guidelines for keratinocyte cancer.
- Hughes M, van der Pols C, Marks G et al 2006. Food intake and risk of squamous cell carcinoma of the skin in a community: The Nambour skin cancer cohort study. International Journal of Cancer. Volume 119, issue 8, 15 October 2006, pages 1953-1960. 2006
- Skin Cancer Council Australia 2016. Skin cancer types, in Skin cancer statistics and issues.
- Butler G, Neale R, Green A et al, 2005. Nonsteroidal anti-inflammatory drugs and the risk of actinic keratoses and squamous cell cancers of the skin. Journal of the American Academy of Dermatology. Volume 53, issue 6, pages 966-972, 1 December 2005.
- Green A, Williams G, Neale R et al 1999. Daily sunscreen application and betacarotene supplementation in prevention of basal-cell and squamous-cell carcinomas of the skin: a randomised controlled trial. The Lancet. Volume 354, issue 9180, pages 723-729, 28 August 1999.
- Chen, Andrew C, et al 2015. A phase 3 randomized trial of nicotinamide for skin-cancer chemoprevention. The New England Journal of Medicine. 22 October 2015.
- Ferrell, M., Wang, Z., Anderson, J.T. et al. A terminal metabolite of niacin promotes vascular inflammation and contributes to cardiovascular disease risk. Nat Med 30, 424–434 (2024).
- Nichols A, Allen A, Shareef S et al 2017. Association of human papillomavirus vaccine with the development of keratinocyte carcinomas. JAMA Dermatology. 2017; 153(6): 571-574.
Treatments for squamous cell carcinoma
Time to check for a squamous cell carcinoma?
We can treat pre-cancerous conditions such as solar keratoses, and improve unsightly age spots and vessels at the same time.
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