Squamous cell carcinoma

SCC is a common skin cancer, especially in older people. It causes a crusty or scaly lump or patch. It's usually easily treated, but sometimes spreads.

Also known as

SCC, keratoacanthoma

Symptoms and signs

  • Pink scaly patch or sore that does not heal
  • Sore or tender lump with a crust on top

Risk factors

  • Medical conditions affecting the immune system, e.g. HIV/AIDS, some forms of lymphoma
  • Medications that suppress the immune system, e.g. for inflammatory bowel diseases or to prevent organ transplant rejection
  • Smoking
  • Human papillomavirus infection

Prognosis / outcome

Progression

Prevention of

 

Squamous cell carcinoma

  • Minimise excessive ultraviolet exposure (e.g. sunscreen, hats, clothing, shade)
  • Nicotinamide (vitamin B3) taken orally can reduce the risk of future squamous cell carcinomas by 25 per cent.
  • Discontinue smoking; If possible, discontinue medications that increase SCC risk

More information

Recommended web links

Clinical images of
Squamous cell carcinoma
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Squamous cell carcinoma, also known as SCC or intraepithelial carcinoma, is a common skin cancer, especially frequent in fair-skinned older people. SCC usually grows on sun-exposed parts of the body without causing serious medical problems, but it can spread to other parts of the body in some cases.  If diagnosed early, squamous cell carcinoma is easily treated, but a small percentage of cases can be fatal.

Cause

99 per cent of squamous cell carcinomas are caused by ultraviolet (UV) radiation from sun exposure (cancer Council 2016). UV radiation damages DNA in cells, so that they no longer grow correctly and skin cancer can develop (AIHW 2016). Squamous cell carcinoma is caused by cumulative long term sun exposure over many decades (Leiter 2008), including in adulthood and later life, meaning that people who work outside are at higher risk (Cancer Council 2020).

In some cases, the human papilloma virus (HPV), which causes warts and cervical cancer, appears to act together with sun exposure to lead to development of SCC (Cancer Council 2018).

Statistics

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 (cancer Council 2020). Squamous cell carcinoma is more common with increasing age, with the vast majority occurring in people aged 55 and above (Cancer Council 2018). Males are approximately one and a half times more likely to develop SCC than females (AIHW 2016).

Each year in Australia, over 600 people die from SCC (Cancer Council 2016).

Risk factors

Major risk factors for developing squamous cell carcinoma are:

  • Previous squamous cell carcinoma or basal cell carcinoma: Up to 60 per cent of people with one of these non-melanoma skin cancers develop another in the next three years (RACGP 2018)
  • 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 arsenic (Centeno 2002)
  • Fair complexion, a tendency to burn rather than tan, the presence of freckles, light eye colour, light or red hair colour
  • Age > 40 years
  • Male
  • Presence of multiple solar keratoses
  • High levels of ultraviolet exposure such as outdoor workers: Outdoor workers have up to 5 times higher risk compared with people who have only worked indoors (Cancer Council 2020).
  • 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 (cancer Council 2020)
  • Smoking, in particular for SCC of the lip. Current smokers are up to three times more likely to develop SCC than non-smokers (Whiteman 2019).

Symptoms and signs of squamous cell carcinoma

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 (Rawlin 2019). 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) (Cancer Council 2016).

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.

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 (Cancer Council 2016b).

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 (Rawlin 2019).

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 (Cancer Council 2018).

Different types of SCC progress in other ways.

  • Superficial SCC (also called Bowen's disease 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 does not always happen, so it is usually treated by surgical removal.

Treatment

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 (Cancer Council 2018).

Bowen's disease affects only the upper part of the skin and can be treated from the surface using cryotherapy (freezing) or fluorouracil, a chemotherapy cream. Each of the treatment options has advantages and disadvantages and should be discussed with a doctor.

Prevention

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 SC 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 SCC (Hughes 2006), and one study has found lower rates of SCC in people who regularly take non-steroidal anti-inflammatory drugs such as aspirin (Butler 2005).

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 (Green 1999).

Vitamin B3 (taken in the form of nicotinamide 1000mg daily) reduces the development of future squamous and basal cell carcinomas by 23 per cent (Chen 2015).

There are case studies of HPV vaccine being successfully used to treat and prevent the recurrence of SCC in patients unsuitable for surgical treatment (Nichols 2017).

References

Cancer Council Australia
Sunsmart national position statement: sun exposure and vitamin D - risks and benefits
Cancer Council position statements
2016
https://wiki.cancer.org.au/policy/Position_statement_-_Risks_and_benefits_of_sun_exposure
Date accessed:
July 4, 2021
Australian Institute of Health and Welfare
Skin cancer in Australia
2016
https://www.aihw.gov.au/reports/cancer/skin-cancer-in-australia/contents/table-of-contents
Date accessed:
July 4, 2021
Leiter U, Garbe C
Epidemiology of melanoma and nonmelanoma skin cancer: the role of sunlight
Advances in Experimental Medicine and Biology, vol. 624, pp. 89–103
2008
https://link.springer.com/chapter/10.1007%2F978-0-387-77574-6_8
Date accessed:
July 4, 2021
Cancer Council
Risk factors/epidemiology
Skin cancer statistics and issues
2020
https://wiki.cancer.org.au/skincancerstats/Risk_factors/epidemiology
Date accessed:
July 4, 2021
Cancer Council Australia
Optimal care pathway for people with keratinocyte cancer (basal cell carcinoma or squamous cell carcinoma), second edition
Optimal cancer care pathways
2021
https://www.cancer.org.au/assets/pdf/keratinocyte-cancer-basal-cell-carcinoma-or-squamous-cell-carcinoma-2nd-edition
Date accessed:
November 21, 2021
Cancer Council Australia
Skin cancer incidence and mortality
Skin cancer statistics and issues
2016
https://wiki.cancer.org.au/skincancerstats_mw/index.php?title=Skin_cancer_incidence_and_mortality&oldid=630
Date accessed:
July 4, 2021
Royal Australian College of General Practitioners
Skin cancer
"Red Book" guidelines for preventive activities in general practice
2018
https://www.racgp.org.au/clinical-resources/clinical-guidelines/key-racgp-guidelines/view-all-racgp-guidelines/guidelines-for-preventive-activities-in-general-pr/early-detection-of-cancers/skin-cancer
Date accessed:
July 4, 2021
Centeno JA, Mullick FG, Martinez L, et al
Pathology related to chronic arsenic exposure
Environmental Health Perspectives. 2002;110 Suppl 5(Suppl 5):883–886
2002
https://doi.org/10.1289/ehp.02110s5883
Date accessed:
July 4, 2021
Whiteman D, Green A, Olsen C
Epidemiology of cutaneous squamous cell carcinoma
Clinical practice guidelines for keratinocyte cancer
2019
https://wiki.cancer.org.au/australia/Guidelines:Keratinocyte_carcinoma/Epidemiology_SCC
Date accessed:
July 4, 2021
Rawlin M, Reid C et al
Clinical features of cutaneous squamous cell carcinoma and related keratinocyte tumours
Clinical practice guidelines for keratinocyte cancer
2019
https://wiki.cancer.org.au/australia/Guidelines:Keratinocyte_carcinoma/Clinical_features_SCC_and_other_related_tumours
Date accessed:
July 4, 2021
Hughes M, van der Pols C, Marks G et al
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
https://doi.org/10.1002/ijc.22061
Date accessed:
July 4, 2021
Skin Cancer Council Australia
Skin cancer types
Skin cancer statistics and issues
2016
https://wiki.cancer.org.au/skincancerstats_mw/index.php?title=Skin_cancer_types
Date accessed:
July 4, 2021
Butler G, Neale R, Green A et al
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
2005
https://doi.org/10.1016/j.jaad.2005.05.049
Date accessed:
July 4, 2021
Green A, Williams G, Neale R et al
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
1999
https://doi.org/10.1016/S0140-6736(98)12168-2
Date accessed:
July 4, 2021
Chen, Andrew C, et al
A phase 3 randomized trial of nicotinamide for skin-cancer chemoprevention
The New England Journal of Medicine. 22 October 2015
2015
https://www.nejm.org/doi/full/10.1056/NEJMoa1506197
Date accessed:
May 8, 2021
Nichols A, Allen A, Shareef S et al
Association of human papillomavirus vaccine with the development of keratinocyte carcinomas
JAMA Dermatology. 2017; 153(6): 571-574
2017
https://doi.org/10.1001/jamadermatol.2016.5703
Date accessed:
July 4, 2021