Squamous cell carcinoma is the second most common type of skin cancer after basal cell carcinoma, the other type of non-melanoma skin cancer, and forms on the squamous cells of the skin’s outermost layer, the epidermis. When diagnosed and treated early, squamous cell carcinomas are not harmful, however if allowed to progress, this cancer can spread and become fatal.

The primary cause of squamous cell carcinoma is sun damage caused by exposure to radiation from the sun’s harmful UV rays. Exposure to arsenic or coal tar products may also cause squamous cell carcinoma, although this is less common.

Those most at risk for developing squamous cell carcinoma are men over 50, as well as those with have fair or light skin, red or blonde hair and green, blue or gray eyes. Smoking, a history of skin cancer, certain genetic disorders and a weakened immune system may also put you at greater risk for developing squamous cell carcinoma.

Additionally, researchers suspect that certain types of human papillomavirus (HPV) may be linked to development of squamous cell carcinoma.

Squamous cell carcinoma typically appears on body areas most frequently exposed to the sun, such as the face, lips, ears, neck, arms and hands. Lesions or nodules may form when squamous cells become cancerous, and they may be raised or flat, red or white in color and appear as crusted or scaly patches, ulcers or non-healing sores.

Actinic keratoses are often mistaken for squamous cell carcinoma, however occurrences of actinic keratosis may develop into skin cancer over time.