Skin Cancer Types
What Is Skin Cancer?
Cancer is tissue which grows at an uncontrollable and unpredictable rate. In the skin, there are three main forms: basal cell carcinoma (or epithelioma), squamous cell carcinoma, and malignant melanoma. The names refer to the cell types in the top skin layer (the epidermis) from which these cancers are derived.
Is It Dangerous?

The most common types of skin cancer are basal cell carcinoma and squamous cell carcinoma. Both types enlarge from the point where they first occur and usually do not spread (metastasize) to distant parts of the body. If not completely removed, both frequently will invade and destroy structures in their paths. Compared to other forms of cancer, these types of skin cancer are generally recognized in their early stages and are therefore easily cured.

Malignant melanoma, on the other hand, may be life threatening if not treated early. It usually appears as a brownish-black spot or bump on the skin which enlarges and sometimes bleeds. Sometimes melanomas arise in moles which have been present for many years.

What Causes Skin Cancer?

The cause of skin cancer, like other forms of cancer, is not completely known. Excessive exposure to sunlight is the single most important factor associated with the development of skin cancers, which develop most commonly on the face and the arms (the most sun-exposed parts of the body). Fair-skinned individuals develop skin cancer more frequently than dark-skinned individuals, and skin cancer, unlike cancer of other organs, is rare in Blacks and Asians. Cancers of the skin are more common in the southern United States.

Skin cancer also tends to be hereditary and occurs very frequently in certain ethnic groups, especially those with fair complexions such as Northern Italians and Celtics (especially Irish). The Boston Irish, even though they live in the northern United States, have a higher rate of skin cancer than Italians living in southern Italy.

Other possible causes of skin cancer include x-rays, trauma, virus infection, smoking, and certain chemicals. There are numerous studies going on today to elucidate these and other possible causes.

How Does Skin Cancer Start?

Skin cancer begins in the uppermost layer of the skin (the epidermis) and grows to the sides on the surface of the skin and downward with roots; these can be compared to the roots of a tree. The persistence of certain skin cancers can also be thought of as the persistence of weeds which will continue to grow unless all the roots are completely removed.

Unfortunately, these rootlike extensions cannot be directly visualized. Therefore, what is apparent to the naked eye on the surface of the skin may actually be only the visible "tip of the iceberg."

© Richard G. Bennett, M.D. 2003