Last updated: April 2024
What is squamous cell carcinoma?
Squamous cell carcinoma (SCC) is one of the most common forms of skin cancer, with only basal cell carcinoma (BCC) occurring more frequently. It starts from cells in the outermost layer of the skin which start to overgrow and potentially spread. SCC can also start from cells on the lips, tongue, lining of the mouth and genitals.
Who gets squamous cell carcinoma?
SCC occurs mainly in Caucasians. Individuals who are immunosuppressed such as those who have had an organ transplant or those with conditions such as lymphoma are more prone to developing multiple SCCs.
SCC usually occurs in older individuals and is very rare in children and young adults.
What causes squamous cell carcinoma?
SCC is caused mainly by chronic sun exposure. It is thought that the ultraviolet light, particularly UVA, from the sun gradually triggers the skin cells to develop into a SCC. This means that most SCCs occur on sun-exposed sites.
Sometimes a wart virus can trigger changes in the cells causing a SCC to form, especially on the genitals or inside the mouth. Other cases are caused by exposure to chemicals (such as arsenic or the tar found in cigarette smoke) or due to trauma such as a burn.
What does squamous cell carcinoma look like?
SCC can present in many different ways. It often presents as a raised scaly lump on sun-exposed sites commonly found on the backs of the hands, forearms, legs, scalp, ears and lips. SCC can also appear as a crusted sore. On the lips an SCC can present as a persistent small ulcer or thickened firm scaly skin.
SCC can develop slowly over years from a red scaly sunspot that slowly thickens and enlarges, to become an intraepidermal carcinoma (Bowen’s disease) which is SCC in the thin top layer of the skin. This may progress further to become a fully developed SCC involving the deeper layers of the skin.
SCC can also develop rapidly with the changes occurring over a few months.
Figure 1. SCC on the forehead – Image reproduced with permission of Dr Brad Jones
Figure 2. SCC on the forehead – Image reproduced with permission of Dr Brad Jones
Figure 3. SCC on the scalp – Image reproduced with permission of Dr Brad Jones
Figure 4. SCC on the elbow – Image reproduced with permission of Dr Brad Jones
Figure 5. SCC on the forearm – Image reproduced with permission of Dr Brad Jones
How is squamous cell carcinoma diagnosed?
The diagnosis is usually made clinically based on the appearance or behaviour of the SCC.
A small biopsy is often needed to confirm the diagnosis prior to treatment being undertaken. The biopsy helps avoid unnecessary surgery on a benign lesion that may mimic SCC and also determines the type of SCC and subsequent treatment method.
How is squamous cell carcinoma treated?
Treatment options will vary depending on the individual and their needs.
The condition is usually treated with simple skin surgery. This enables the pathologist to check under the microscope that the SCC has been removed completely. Further surgery or radiation therapy may be required if there was any residual tumour evident, or nerves were involved, or a more aggressive pattern was seen under the microscope.
In some situations and locations, small SCCs can be treated by a scraping called curettage or by freezing with liquid nitrogen. In cases, where surgery is not appropriate the SCC may be treated by radiation therapy alone. Regular follow-up for monitoring is required.
Cemiplimab (immunotherapy agent) is often used by oncologists for metastatic or locally aggressive SCC.
Evidence shows that taking a daily Vitamin B3 tablet (nicotinamide) may help lower the incidence of SCCs in high risk individuals. 1
What is the likely outcome of squamous cell carcinoma?
Most SCCs can be easily treated and do not cause any future concerns. However, SCCs have the potential to spread to the lymph nodes and other organs.