What Is Skin Cancer?

What is skin cancer? It may seem obvious, but this form of cancer is a unique one because it is the only one that involves the outside of your body.

Skin cancer is, obviously, cancer, a malignant tumor, which involves the skin. Like other forms of cancer, it is comprised of cells which begin growing uncontrollably, forming a tumor.

The skin is part of the integumentary system. The integument covers our body, protects it from the outside environment, prevents loss of body water, aids the immune system and helps control body temperature. Skin cancer generally originates from the outmost layer of the integument, called the epidermis.

True primary skin cancer arises in the skin itself, when cells in the skin suffer genetic damage (mutations) and begin growing as a malignant tumor. However, other forms of cancer that originated elsewhere can involve the skin, either by spreading to the skin (metastasis) or growing into the skin from nearby structures. These other types of cancer which can rarely involve the skin are not discussed in this section. Here we will focus on primary skin cancers which originate whtin the skin cancer.

When answering "What is skin cancer?" it should be made clear that there is no one type of cancer which is called skin cancer. The term skin cancer is a general one for all cancers which originate in the skin. However, there are subtypes of skin cancer which vary quite substantially. Therefore, not all "skin cancer" is created equal. The three most common forms of skin cancer include squamous cell carcinoma, basal cell carcinoma and melanoma, which all vary in their appearance, pathology and their potential affect on the patient. You can learn more about them on the Types of Skin Cancer page.