What Is Melanoma?

The Melanoma Book
by Howard L. Kaufman, M.D., FACS

(Page 2 of 5)

The moment you or a loved one has been diagnosed with melanoma, questions begin to crowd out almost all other thoughts: What does melanoma mean? What's the difference between it and other skin cancers? What are the implications for me and my family? Before you can begin to grasp the diagnosis and start the recovery process, you need clear answers.

The good news is that most melanomas are found early, and the cure rate is approximately 85 percent in these cases. Even when melanoma is found in the advanced stages, treatments can often be remarkably successful.

Simply stated, melanoma is a type of skin cancer that arises from the melanocytes, one particular type of skin cell. Melanoma occurs when the melanocytes become severely abnormal, start dividing uncontrollably, and eventually spread to other parts of the body, sometimes resulting in death.

Most of our cells grow and divide continually. This process is essential for replacing old and worn-out cells, such as on the surface of the skin. The critical balance of cell growth, division, and death is tightly regulated by the genes, which are made up of a substance called DNA. When the DNA is altered, the normal life cycle of cells becomes impaired or out of control. Uncontrolled division of cells results in the growth of a tumor ('tumor' comes from the Latin word for 'mass').

Many things can cause alterations or mutations in DNA, including hereditary factors, exposure to radiation and ultraviolet light, certain toxic chemicals (such as tobacco), and certain viruses. Whatever the cause of the mutations, if the cells continue to divide without stopping, a growth or mass will form: cancer. When this process occurs in the skin, it is called skin cancer.

The severity of the disease is also determined by the ability of the cells to grow into a large size and then spread to other parts of the body, a process called metastasis. Cancers that are more aggressive in their growth and can spread to other parts of the body are called malignant. Cancers that remain small in size and do not spread are called benign, and generally behave in a less threatening manner. This is true not just for skin cancers, but for all cancers in the body.

The names of different forms of cancer are based on their classification as benign or malignant. Benign cancers usually end with the suffix '-oma,' such as lipoma, which refers to a benign growth of fat cells that occurs just under the skin. In contrast, malignant cancers are often called 'carcinomas,' such as breast carcinoma or colon carcinoma. Melanoma is one of the few exceptions to this rule, reflecting the early misconception that melanomas were benign cancers with little tendency to spread. When it became clear that melanomas could grow to large sizes and could spread to almost any other organ in the body, the medical term was changed to malignant melanoma in order to denote the more serious nature of this type of cancer.

Although this book focuses on malignant melanoma, many other kinds of skin cancer exist. These other skin cancers are much more common and usually are easier to cure than melanoma. The type of skin cancer and its severity depends on which cell is the source of the cancer. So in order to understand melanoma and other skin cancers, it's helpful to put them in the context of the normal structures and cells of the skin.

The Structure of the Skin

While its primary function is to protect the body from invading germs, chemicals, water, temperature, and other conditions or irritating substances, the skin also performs other vital functions including:

• regulating body temperature
• fighting infections in conjunction with the body's immune system
• protecting us from ultraviolet damage by the sun
• regulating Vitamin D metabolism

The skin is a complex body organ comprised of two major layers: the epidermis and the dermis. Each of these two main layers contains highly specialized skin cells arranged in sub-layers.

The Epidermis

The epidermis, the layer closest to the skin's surface, contains five sub-layers, or strata. The outermost sub-layers provide a critical protective barrier for the body (see Table 1-1). Generally considered 'dead' because their cells do not divide, these outermost layers continually slough off. Cells in the deepest sub-layer (the stratum basale) divide and replace the cells in the outer layers, completely renewing the skin every twenty-five to fifty days.

Melanocytes are specialized cells that produce melanin, the dark brown pigment responsible for darkening the skin. Melanocytes are located in the deepest epidermal sub-layer (the stratum basale). In response to direct sunlight, these cells produce melanin, which causes the skin to become darker and is visible to the human eye as tanning. Melanin also helps protect against ultraviolet radiation and sun damage.

The activity of the melanocytes determines the natural color of the skin. In other words, your skin color depends not on the number of melanocytes present, but on how much melanin they make.

Table 1-1. The five layers of the epidermis and their function

Layer of the Epidermis	Function
Stratum corneum	Outermost layer; protects the body from external forces
Stratum lucidum	Provides cells and keratin for the outer layers of skin
Stratum granulosum	Produces proteins that cement the skin and helps protect the body from water and other outside forces
Stratum spinosum	Provides a layer of strong attachments that prevents abrasions of the skin
Stratum basale	Innermost layer of epidermis, where melanocytes are located; provides a source for cells in the outer layers of epidermis

The Dermis

The dermis is the larger, inner layer of the skin and, like the epidermis, contains sub-layers (see Table 1-2). To better understand melanoma, it is important to know that the deeper (reticular) layer contains blood vessels, lymphatic vessels, and larger nerves of the skin. The vessels in this layer can pick up specialized cells including melanoma cells and carry them to the lymph nodes. From there, melanomas may travel through the lymphatic and vascular systems and cause cancers in almost any other part of the body.

Table 1-2. The two layers of the dermis and their function

Layer of the Dermis	Function
Papillary dermis: thin layer	Contains papilla that hold the epidermis and dermis together
Reticular dermis: thick layer	Contains blood vessels involved in regulation of temperature Contains sweat glands for temperature control and pheromone release Contains nerve endings and specialized cells that regulate the sense of touch Contains hair follicles and sebaceous glands

Copyright © 2005 Howard L. Kaufman, M.D., FACS

About the Author

Dr. Howard L. Kaufman is founder and Co-Director of the Columbia University Melanoma Center, attending physician at The New York Presbyterian-Columbia University Medical Center, chief of surgical oncology, and associate professor of surgery at Columbia University College of Physicians and Surgeons. He has conducted numerous clinical research trials on vaccines for cancer, lectures widely on cancer treatment and has published more than 100 articles in the field of tumor immunology and immunotherapy. He lives in New York City.