Cancer Types – Skin Cancer (Non-Melanoma)
Skin Cancer (Non-Melanoma): Overview
About the skin
The skin, the body’s largest organ, protects against infection and injury and helps regulate body temperature. The skin also stores water and fat and produces vitamin D. Skin is made up of two main layers: the epidermis (outer layer of skin) and the dermis (inner layer of skin). See the Medical Illustrations section for a drawing of these layers.
Types of skin cancer
Cancer begins when normal cells change and grow uncontrollably, forming a mass called a tumor. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body). There are three main types of skin cancer:
Basal cell carcinoma. Cells in the lower epidermis are round cells known as basal cells. About 80% of skin cancer develops from this type of cell and is called basal cell carcinoma. Basal cell carcinoma most often develops on the head and neck. It is mainly caused by sun exposure or develops in people who received radiation therapy as children. This type of skin cancer usually grows slowly and rarely metastasizes (spreads) to other parts of the body.
Squamous cell carcinoma. Most of the epidermis is made up of flat, scale-like cells called squamous cells. Approximately 20% of skin cancer develops from these cells and is called squamous cell carcinoma. This type of cancer is mainly caused by sun exposure, but it can appear on skin that has been burned, damaged by chemicals, or exposed to x-rays. Sites of a chronic inflammatory skin condition, mucous membranes (skin that lines the mouth, nose, anus, and a woman’s vagina), and the lips are susceptible to squamous cell carcinoma. Squamous cell carcinoma rarely metastasizes, but it is more likely to spread than basal cell carcinoma.
Melanoma. Where the epidermis meets the dermis, there are scattered cells called melanocytes, which produce the pigment melanin that gives skin color. Melanoma starts in melanocytes, and it is the most serious type of skin cancer. For more information about melanoma, please visit the melanoma section.
Basal cell carcinoma and squamous cell carcinoma are generally grouped together and called non-melanoma skin cancers to distinguish them from melanoma, which develops from very different cells and is treated differently because it is more likely to spread than other skin cancers. Typically, non-melanoma skin cancers can be treated with relatively simple surgery. If the cancer is very small, medicated creams prescribed by a doctor, cryosurgery (freezing) or laser surgery may be used. Learn more in the Treatment Options section.
There are a few other rarer types of skin cancer, including keratoacanthomas, Merkel cell carcinoma, cutaneous (skin) lymphomas, Kaposi sarcoma, skin adnexal tumors, and sarcomas, all of which are classified as non-melanoma skin cancers. However, this section focuses on basal cell and squamous cell skin cancers.
Read more about skin cancer (non-melanoma) here.