This page was reviewed under our medical and editorial policy by
Frederick L. Durden, Jr, MD, Plastic and Reconstructive Surgeon & Microsurgical Reconstructive Surgeon
This page was updated on October 20, 2022.
In 2021, the National Cancer Institute (NCI) estimates 106,110 people in the United States will be diagnosed with melanoma, a type of skin cancer that affects pigment cells, or melanocytes. These cells help give skin its color.
Melanoma isn’t the most common type of skin cancer, but it’s among the most dangerous due to its tendency to grow and spread. It’s also been steadily on the rise in the past few decades. Still, the overall prognosis of melanoma is good, with a 93.3 percent five-year relative survival rate, according to the NCI. This means that 93.3 percent of people are still alive five years after they’re diagnosed with melanoma.
About 2.3 percent of people in the United States are diagnosed with melanoma at some point in their life, though most people are diagnosed between ages 65 and 74, according to the NCI.
Out of more than 30 different types of melanoma, the most common is superficial spreading melanoma.
Superficial spreading melanoma is the most common subtype of melanoma skin cancer, accounting for about 70 percent of cases, according to the NCI.
The name may be long, but it hints at how this type of cancer behaves. “Superficial” refers to the horizontal growth pattern of cancer cells. When it develops, superficial spreading melanoma tends to spread slowly outward but remains for quite a while (sometimes years) in the same layer of the epidermis where it began before invading other layers of tissue.
Superficial spreading melanomas may develop anywhere on the skin, but they tend to be found in different places on men and women.
In women, they tend to show up on the legs.
In men, they tend to develop on the:
Superficial spreading melanomas tend to be:
These melanomas may have indentations within the lesion as well. The average size of a superficial spreading melanoma is about 20 mm, or 2 cm, across.
None of these characteristics make superficial spreading melanoma appear dramatically different from other types of melanoma when seen with the naked eye.
Thus, a good practice for prevention or early diagnosis of any type of melanoma is to take note of changes in the skin with any new or existing moles regarding:
All types of melanoma are caused by slight changes in genetic material called gene mutations. Some gene mutations are inherited—they may run in the family and be present from birth. Others are ones that develop over time due to different factors. For example, ultraviolet (UV) rays from the sun penetrate a person’s DNA and cause slight changes in the genes. As the cells naturally grow and divide, they may pass on these mutations to new cells.
In melanomas caused by a gene inheritance, researchers have identified the specific gene mutations that lead to melanoma. These include the BRAF oncogene, which is responsible for about half of all melanomas, as well as the genes NRAS, CDKN2A, NF1 and CDK4.
Several characteristics increase the chances of developing superficial spreading melanoma. Knowing the risk factors for cancer may help doctor and patient discuss steps for cancer prevention.
The risk factors for melanoma include:
If a patient has a suspicious patch of skin that shows any sign of cancer, there’s typically a standard set of steps that follow.
Doctors may look for any other signs of skin cancer across the body, including feeling the lymph nodes, especially the ones closest to the suspicious spot. Cancer may affect nearby lymph nodes, making them larger.
In order to know if a spot is cancerous, doctors may need to take a sample of tissue, called a biopsy, and inspect the cells. They may remove all suspicious spots detected.
There are a few different ways to perform a skin biopsy.
Other types of biopsies, such as shave biopsies or incisional biopsies, in which only a part of a tumor is removed, may be used to diagnose melanoma but aren’t as common.
After the biopsy, a pathologist looks at the removed tissue under a microscope and may be able to tell right away if the sample shows melanoma or not. The pathologist may also need to do additional tests to confirm melanoma or to confirm which genes have mutated to cause the melanoma.
Additional imaging tests may be done if a doctor is concerned that the melanoma has spread. These may include:
Results from any or all of these tests guide doctors in staging a melanoma, or figuring out how much it has spread, if any.
The most common treatment for most superficial spreading melanoma is to have it removed surgically. This may or may not include having surgery to remove affected lymph nodes as well.
Even for melanoma that has spread to distant parts of the body, surgery may be able to remove cancer from those sites. Treatment for advanced melanoma may include systemic drug therapy—such as chemotherapy, immunotherapy or targeted therapy—as well.
If melanoma returns after treatment, called recurrent melanoma, part of the treatment may involve injecting a cancer-targeting virus into the melanoma lesion itself. Through this therapy, called oncolytic therapy, a virus works in tandem with the body’s immune system to fight cancer cells.
The treatment plan depends on several factors. Along with a cancer care team, the patient must take into account:
When compared with the survival rates of all melanomas together, superficial spreading melanoma survival rates tend to be slightly higher, regardless of the stage at diagnosis. The five-year survival rate represents the percentage of people still alive five years after a cancer diagnosis.
According to a 2016 study in BMC Cancer, the survival rates for superficial spreading melanoma are:
While the survival rates of superficial spreading melanoma are promising overall, there’s still a lot about this type of melanoma—and others—that researchers don’t know yet.
In general, the two most common types of melanoma, superficial spreading and nodular, were thought to be different only in their initial directions of growth. Superficial spreading melanoma grows outward, spreading across the epidermis at first and may take years to invade other tissue layers, while nodular melanoma immediately spreads into different layers of surrounding tissue.
However, a research review from 2012 in Melanoma Research shows that there may be more complex genetic distinctions between these two types of melanoma than were previously realized, which may aid in the development of additional treatment approaches.