Squamous cell carcinoma (SCC) is a health condition involving the uncontrolled growth of abnormal cells in the skin outer squamous cells of the epidermis. It occurs as a result of keratinization of the epidermal cells and has the potential to metastasize to other regions of the body.
The presentation of squamous cell carcinoma can occur on any area of the body, but is most common in areas that are frequently exposed to ultraviolet (UV) radiation, such as the ears, lips, face, neck, head, arms and legs. Distinctive signs on the skin can help to diagnose the condition, including:
- Red, scaly patches
- Open sores
- Elevated growths with depressed center
- Crusting or bleeding of the area
SCC can be classified as either “in situ” confined to the localized site, or “invasive” involving the surrounding tissues and may spread to other organs in the body. Non-invasive carcinoma may also be referred to as Bowen’s disease.
Skin cancers have a higher incidence than any other type of cancer that continues to rise, despite knowledge and public health campaigns about their prevention. Squamous cell carcinoma is the second most common type of skin cancer, after basal cell carcinoma.
In the United States, approximately 700,000 cases of squamous cell carcinoma are diagnosed each year and the incidence has been following an upward trend.
Men are more likely to be affected than females, which is thought to be linked to greater exposure to ultraviolet (UV) radiation, particularly to the head and neck area.
Causes and Risk Factors
Exposure to UV radiation appears to carry the greatest risk of squamous cell carcinoma and is seen as the primary cause of the condition. Additionally, individuals with fair skin are more susceptible to the damage caused by UV radiation.
For this reason, people with fair skin living in areas with high sun exposure, such as the predominantly Caucasian population of Australia, are most likely to get squamous cell carcinoma. Regions in the equatorial zones tend to have particularly high levels of UV radiation.
Additionally, there are some other risk factors that may lead to the condition. These include:
- Chemical carcinogens (e.g. arsenic, chromium, soot, tar)
- Infection with human papillomavirus
- Exposure to ionizing radiation
- Chronic inflammation surrounding ulcers or sinuses
- Xeroderma pigmentosum
As squamous cell carcinoma is a relatively common condition with potentially serious outcomes, there have been considerable public health and educational campaigns in recent decades to reduce the incidence of the disease.
It is important that populations at risk – particularly those with fair skin living in areas with high UV radiation exposure – are aware of ways to reduce the risk of the condition.
This includes avoiding excessive sun exposure in the problematic times of the day, usually between 11 am and 3 pm, by staying indoors or in the shade. Wearing appropriate clothing and sunscreen to protect skin while in direct sunlight is also recommended to help prevent the condition.
Signs of early development of Bowen’s disease should be widely known to allow early diagnosis, intervention and management of the disease.
There are several other conditions that may present with similar symptoms to squamous cell carcinoma and require differential diagnosis. These include:
- Keratoacanthoma – mild malignancy of the skin with a central keratin plug, originating from the pilosebaceous glands
- Marjolin’s ulcer – distinct type of SCC that arises from ulcer or burn wound that failed to heal normally
- Basal cell carcinoma
- Malignant melanoma
- Solar (actinic) keratosis
- Pyogenic granuloma
- Seborrhoeic or plantar warts