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Melanoma is a type of skin cancer that develops when melanocytes (the cells that give the skin its tan or brown color) start to grow out of control.
Melanoma is much less common than some other types of skin cancers. But melanoma is more dangerous because it’s much more likely to spread to other parts of the body if not found and treated early.
Most skin cancers start in the top layer of skin, called the epidermis. There are 3 main types of cells in this layer:
The epidermis is separated from the deeper layers of skin by the basement membrane. When a skin cancer becomes more advanced, it generally grows through this barrier and into the deeper layers.
Melanoma is a cancer that begins in melanocytes.
Most melanomas start in the skin. Another name for these cancers is cutaneous melanoma.
Melanomas can start anywhere on the skin, but in people with lighter skin color they are more likely to start on the trunk (chest and back) in men and on the legs in women. The neck and face are other common sites.
People with darkly pigmented skin have a lower risk of melanoma at these more common sites.
There are different types of skin melanoma. The most common types are:
Melanomas can also form in other parts of the body, such as:
These are much less common than melanoma of the skin.
There are many other types of skin cancer. Skin cancers that are not melanomas are sometimes grouped as non-melanoma skin cancers because they develop from skin cells other than melanocytes. They tend to behave very differently from melanomas and are often treated with different methods.
Basal cell cancer (BCC) and squamous cell cancer (SCC) are by far the most common types of skin cancer. In fact, they are more common than any other form of cancer in the United States. These cancers (especially BCCs) are much less likely to spread (metastasize) to other parts of the body than are melanomas, so they are usually less concerning and are treated differently. These cancers are discussed in Basal and Squamous Cell Skin Cancer.
Other types of non-melanoma skin cancer are much less common than basal and squamous cell cancers and are treated differently. They include:
Together, these types account for less than 1% of all skin cancers.
Many types of benign (non-cancerous) tumors can develop from different types of skin cells.
A mole (nevus) is a benign skin tumor that develops from melanocytes. Almost everyone has some moles. Nearly all moles (nevi) are harmless, but having some types can raise your risk of melanoma. See Risk Factors for Melanoma Skin Cancer for more about moles.
A Spitz nevus is a kind of mole that sometimes looks like melanoma. It’s more common in children and teens, but it can also be seen in adults. These tumors are typically benign and don’t spread. But sometimes doctors have trouble telling Spitz nevi from true melanomas, even when looking at them under a microscope. Therefore, they are often removed, just to be safe.
Most of these tumors rarely, if ever, turn into cancers. There are many other kinds of benign skin tumors, but most are not very common.
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
Curiel-Lewandrowski C. Melanoma: Epidemiology and risk factors. UpToDate. 2023. Accessed at https://www.uptodate.com/contents/melanoma-epidemiology-and-risk-factors on September 6, 2023.
Mitchell TC, Karakousis G, Schuchter L. Chapter 66: Melanoma. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff’s Clinical Oncology. 6th ed. Philadelphia, Pa: Elsevier; 2020.
Ribas A, Read P, Slingluff CL. Chapter 92: Cutaneous Melanoma. In: DeVita VT, Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg’s Cancer: Principles and Practice of Oncology. 11th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2019.
Swetter S, Geller AC. Melanoma: Clinical features and diagnosis. UpToDate. 2023. Accessed at https://www.uptodate.com/contents/melanoma-clinical-features-and-diagnosis on September 6, 2023.
Last Revised: October 27, 2023