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Superficial spreading melanoma (SSM) is the most common type of melanoma. It’s estimated that 7 out of every 10 people diagnosed with melanoma have SSM. In most people, SSM grows slowly along the top layer of the skin.
In this article, we’ll learn more about SSM, who’s at risk, and what it might look and feel like. We’ll also talk about how it’s diagnosed and treated.
SSM is a subtype of melanoma. It begins in the pigment cells of your skin, called melanocytes. This form of melanoma develops in your epidermis, the outermost layer of your skin.
The name “superficial spreading melanoma” describes the way this type of melanoma usually spreads. Instead of spreading to deeper layers of skin, SSM tumors tend to grow slowly outward along the surface of the skin. The tumor can remain in the same layer of skin cells it developed for several years before it begins growing into other parts of the skin.
SSM may develop on any part of your skin. Parts of the body that are most likely to develop this type of melanoma are those that get intense sun exposure at irregular intervals.
The most commonly affected areas are different in males and females, according to DermNet. In females, SSM is most commonly found on the legs. In males, this type of melanoma is most commonly found on the trunk, which includes the head, neck, chest, abdomen (stomach), and back.
If you have SSM, you may find that it looks like other types of melanoma. Most often, SSM develops on skin that previously appeared healthy and without any noticeable changes. About 1 in 4 cases of SSM develop from an existing mole.
Characteristics of an SSM tumor include:
SSM tumors can change quickly. You may notice it grow in a matter of a few weeks or months. When diagnosed, the average size of an SSM tumor is about three-quarters of an inch (20 millimeters) across.
The National Cancer Institute (NCI) estimates that more than 100,000 people will develop melanoma in 2024. About 70 percent, or 70,000, of these people are estimated to be diagnosed with SSM.
Melanoma of all types is caused by a genetic mutation (variation) that makes skin cells grow out of control. Researchers don’t fully understand why some melanocytes begin to grow out of control. Genetic mutations that cause melanoma have been linked to several risk factors, such as:
If you notice an unusual spot on your skin or an atypical mole, the first step is to visit a dermatologist (a health care provider who specializes in treating skin conditions). Your dermatologist will look at the suspicious area (called a lesion) and perform a skin exam to check your entire body for other signs of skin cancer. A skin biopsy can confirm a melanoma diagnosis.
It’s not possible to tell whether a suspicious mole or spot is cancerous just by looking at it.
If your dermatologist is unsure about whether your lesion is cancerous, they may perform a noninvasive type of biopsy called reflectance confocal microscopy (RCM). This procedure allows providers to see deeper layers of skin without cutting out a sample.
If your dermatologist suspects you may have some type of skin cancer, they will likely perform an excision biopsy. During an excision biopsy, the entire lesion plus some surrounding tissue is removed. If your lesion is very large, your provider may perform a punch biopsy, where a small cylinder of skin is cut from the lesion. In most cases, an excision biopsy is preferred. A punch biopsy might miss areas with cancer cells.
Once the tissue sample is taken with a biopsy, it’s sent to a laboratory. In the laboratory, a pathologist (a doctor who specializes in examining body tissues) will examine the tissue sample under a microscope. If the tissue sample is melanoma, the pathologist will determine the stage of your melanoma. Stages 0, 1, and 2 are usually considered early stages where cancer hasn’t spread. Stages 3 and 4 are considered advanced melanoma. (Cancer stages are sometime rendered with Roman numerals, e.g., “stage IV” instead of “stage 4.”) In advanced melanoma, the cancer has spread to other parts of the body.
The pathologist may perform additional testing to find out if the cancer has any specific mutations. This may be helpful in choosing the best treatment.
If the results of your skin biopsy indicate that you have SSM, your health care provider may recommend additional tests to check if the cancer has spread to other parts of your body, called metastasis. Additional tests can also help with melanoma staging.
A sentinel lymph node biopsy is a procedure that checks whether melanoma cancer cells have spread to nearby lymph nodes.
Imaging tests can help spot areas where melanoma may have spread. Examples of imaging tests include magnetic resonance imaging (MRI), computed tomography (CT) scan, and positron emission tomography (PET) scan.
Blood tests can check for substances in your blood associated with metastatic melanoma, such as lactate dehydrogenase (LDH).
You may not need additional testing if you have an early stage of SSM. Talk to your health care provider about which diagnostic tests are best for you.
When diagnosed in the early stages, SSM is usually curable. Your treatment options depend on several factors, including:
Surgery is the most common melanoma treatment for people with early disease. A surgeon will remove the tumor and a margin of healthy-looking skin around the tumor. The amount of skin around the tumor that’s removed depends on the depth of the tumor.
If cancer has spread to your lymph nodes — small, bean-sized organs located throughout the body — nearby lymph nodes also may be removed during surgery. Surgery can also be used to remove tumors due to melanoma spreading. In some cases, you may receive radiation therapy, immunotherapy, or targeted therapy after surgery to prevent cancer recurrence.
Drug treatments for SSM are usually used when cancer has spread to other parts of the body or to prevent cancer from coming back.
Drug treatments for SSM may include:
Early detection of SSM generally leads to a positive prognosis (outlook). The percentage of people still alive five years after their melanoma diagnosis (called the five-year survival rate) for people with any type of melanoma that hasn’t spread is greater than 99 percent. The five-year survival rate for SSM between 2014 and 2018 was 99.5 percent.
Several factors can affect your prognosis, including the stage of melanoma and your age, sex, and race/ethnicity. Talk to your health care provider for more information on your prognosis.
MyMelanomaTeam is the social network for people with melanoma and their loved ones. On MyMelanomaTeam, members come together to ask questions, give advice, and share their stories with others who understand life with melanoma.
Have you been diagnosed with superficial spreading melanoma? What signs and symptoms did you notice? What was your melanoma treatment like? Share your experience in the comments below, or start a conversation by posting on your Activities page.
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Leonora Valdez Rojas, M.D.
received her medical degree from the Autonomous University of Guadalajara before pursuing a fellowship in internal medicine and subsequently in medical oncology at the National Cancer Institute.
Learn more about her here.
Amanda Jacot, PharmD
earned a Bachelor of Science in biology from the University of Texas at Austin in 2009 and a Doctor of Pharmacy from the University of Texas College of Pharmacy in 2014.
Learn more about her here.
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