Squamous cell carcinoma (SCC)
What is a SCC?
Squamous cell carcinoma is a malignant tumour arising from keratinocytes, the predominant cells of the skin surface (epidermis). It is the second commonest skin cancer, behind BCC. Its main cause is excessive and cumulative sun exposure, but immune deficiency considerably increases the risk. It is more frequent in men than women, in fair skin and after the age of 50. SCC’s can occur on any site exposed to the sun and the preferential affected areas are bald scalp, face, neck, forearms, back of the hands and shins. Many arise from pre-existing sunspots (named actinic keratosis or solar keratosis), that are considered precursor or premalignant lesions. Chronic wounds and scarred areas are also at increased risk for developing an SCC.
They appear as scaly, flesh-toned to pale pink, firm and raised spots, that arise on a background of sun-damaged skin. In the evolution, the lesion may become sore, grow rapidly, bleed and ulcerate.
If left untreated, SCC’s have the ability to spread to the lymph nodes and other parts of the body (metastasis), which happens in about 4 out of 100 cases. The risk of metastasis is higher for immune deficient people, such as patients who receive organ transplant, and in certain locations, especially the lips, where SCC may look like a non-healing “sore”.
What is Bowen’s disease?
Bowen’s disease is an early stage, non-invasive or in-situ SCC, which means that malignant cells are restricted to the superficial layer of the skin (epidermis). It is considered a “pre-cancerous” condition. It presents as a slow-growing, symptomless, red or pink scaly patch, usually in sun-exposed areas, that can be mistaken for dermatitis, psoriasis or fungal infection. Early diagnosis and treatment are desirable to prevent Bowen’s disease progression to an invasive SCC. However, in general, its potential for invasiveness is low.
How are SCC diagnosed?
Suspicious lesions are usually detected during skin examination by your doctor. A biopsy may be necessary to confirm the diagnosis. During self-examination, beware of “sunspots” that have become firmer or thicker, painful, inflamed or that stand out when compared to other spots. Non-healing sores on the lips are also a warning sign.
How are SCC treated?
Surgical excision, including a safety margin of normal appearing skin beyond the tumour, is the standard treatment for SCC. Radiotherapy is rarely the treatment of choice, but may be an option in large or rapidly enlarging lesions or in patients where aggressive surgical management may not be tolerated.
Pre-cancerous lesions (Bowen’s disease) may be treated in a more conservative way. In general, most treatment options available for actinic keratosis (sunspots), could be used to treat in-situ SCC’s, as follows:
Curettage and cautery
Cryotherapy (liquid nitrogen)
5-fluorouracil cream (Efudix®)
Imiquimod cream (Aldara®, APO-Imiquimod®)
Ingenol mebutate cream (Picato®)
Photodynamic therapy (PDT)
How can non-melanoma skin cancers be prevented?
NMSC, including BCC, SCC and pre-cancerous sun spots (actinic or solar keratosis), are strongly related to ultraviolet (UV) radiation. The predisposition related to skin colour and ability to tan cannot be changed. However, our behaviour towards sun exposure can always be improved and, ideally, since early childhood. Some protective advices are:
Seek shade and avoid outdoor activities in peak sun-hours (10am to 4pm), but especially around midday;
Wear sun-protective clothes, covering as much skin as possible;
Wear a wide brim hat, that protects head, face and ears;
Wear sunglasses with adequate UV protection (lens categories 2, 3 and 4 – according to Australian/NZ standards);
Apply a thick layer of broad spectrum sunscreen (protection against both UVA and UVB rays, SPF30+ or higher, preferably 50+ in Australia) – 20 minutes before going out, reapplying regularly (every 2 hours and after swimming);
Always remember: there is no “safe tan”!
What is the role of nicotinamide in the prevention of non-melanoma skin cancers?
A clinical trial conducted from 2012-2014 in Australia (ONTRAC Study) showed that taking vitamin B3 (nicotinamide) in high doses (500mg orally twice a day) can prevent NMSC (BCC and SCC). Individuals taking the nicotinamide tablets had 23% less skin cancers comparing to the ones taking placebo. The benefits were higher in participants that had multiple previous skin cancers.
It is a low-cost, safe and effective intervention that has been incorporated into standard recommendations in recent years, especially for people with a past history of multiple NMSC, but not yet available to the general population.
When prescribed nicotinamide by your doctor, beware not to use nicotinic acid tablets, which is another form of vitamin B3. This can cause headache, facial redness and low blood pressure. It is essential, also, to maintain your regular skin checks and general sun protection measures.