Debra Wood, RN
and Michael Jubinville, MPH
Cancer is a disease in which cells grow in an abnormal way. Normally, the cells divide in a controlled manner to replace old or damaged cells. If the cells keep dividing when new ones are not needed, a mass of tissue called a tumor forms.
Not all tumors are cancer, those that are cancer are called malignant. Cancer tumors invade and damage tissue around them. The cancer cells can also enter the lymph and blood streams, spreading to other parts of the body. Melanoma is skin cancer of the melanocytes, the cells that produce skin color and give moles their dark color. Melanoma tends to be an aggressive type of skin cancer. It is also more likely to spread to other parts of the body.
There are 2 main layers of the skin:
Melanocytes appear on the surface of the skin as moles. Most moles are harmless but some may be develop into melanoma. Because melanomas are the bottom layer of the epidermis they can quickly grow down into the dermis. In the dermis the cancer has access to lymph nodes and blood vessels, which then carry cancer cells to other parts of the body. The most common sites for melanoma to spread to are the lungs, liver, brain, bones, and intestinal tract.
Males tend to get melanoma on the torso, the area between the shoulders and hips. Women are more likely to find melanoma on the arms or legs. It is important to note that melanoma can develop anywhere on the body, even those not regularly exposed to the sun, like the genitals, anal area, eyes, or mouth.
Melanoma is categorized by where tumors start, how they grow, and their appearance under a microscope. Four basic types of melanoma include:
This fact sheet focuses on melanomas that affect the skin.
General information about melanoma. National Cancer Institute website. Available at: https://www.cancer.gov/types/skin/patient/melanoma-treatment-pdq. Updated March 10, 2017. Accessed March 16, 2017.
Melanoma. EBSCO DynaMed Plus website. Available at:
http://www.dynamed.com/topics/dmp~AN~T115302/Melanoma. Updated January 10, 2017. Accessed March 16, 2017.
Melanoma. Merck Manual Professional Version website. Available at: http://www.merckmanuals.com/professional/dermatologic-disorders/cancers-of-the-skin/melanoma. Updated February 2017. Accessed March 16, 2017.
What is melanoma skin cancer? American Cancer Society website. Available at:
https://www.cancer.org/cancer/melanoma-skin-cancer/about/what-is-melanoma.html. Updated May 20, 2016. Accessed March 16, 2017.
Last reviewed March 2017 by Mohei Abouzied, MD, FACP
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