Squamous Cell Carcinoma

What Is It?
Squamous cell carcinoma of the skin is one of the three most common types of skin cancer. While it is less common than basal cell carcinoma, the most common form of skin cancer by far, it is somewhat more common than malignant melanoma. It also shares more in common in terms of speed of growth, invasiveness and prognosis with basal cell. This malignant tumor consists of flat (squamous) cells, hence the name.

What Causes It?
Like most other forms of skin cancer, the most common risk factor associated with squamous cell is sun exposure. The UV radiation in sunlight can cause damage to cells and DNA, eventually leading to cancer. The risk is highest for people with light-colored skin, blue or green eye color and blond or red hair. These individuals tend to have the least protection from the potentially damaging sun rays.

In terms of sun exposure, long-term, frequent sun exposure (such as in those people who work outside) is the greatest risk. A history of numerous severe sunburns, particularly if they occurred early in life, is also a risk factor.

Other factors that can contribute to the development of squamous cell carcinoma of the skin include older age, exposure to large number of x-rays, arsenic exposure and exposure to various other chemicals.

Rarely, squamous cell tumors can evolve from a pre-cancerous lesion of the skin called actinic keratosis. These are benign lesions but can rarely develop into cancer.

What Does It Look Like?
In its earliest stages, squamous cell is confined to the outermost layers of skin (called squamous cell carcinoma in situ or Bowen's disease). At this stage, it often appears as a large reddish patch which can be crusted or scaly in appearance.

It will enlarge into a bump over time and can continue to have a rough, scaly surface. Occasionally these can ulcerate in the middle. The most common location for these tumors is on skin which is frequently exposed to the sun, including the head and neck, hands and arms.

What Is The Prognosis?
Squamous cell is somewhat faster growing and more aggressive than basal cell carcinoma. However, it is still relatively slow growing and less invasive, particularly compared to melanoma. It can eventually metastisize (spread to distant tissues) but this typically occurs late.

If caught early and treated (surgically removed) this form of skin cancer holds a relatively good prognosis.