Superficial Spreading Melanoma

Unlike invasive melanoma, which spreads vertically downward into the skin, superficial spreading melanoma grows horizontally and spreads across the skin surface before spreading to deeper layers of the skin. Superficial spreading melanoma is considered an invasive melanoma that has 99+% survival when caught in the early stage.

Changes (mutations) in the DNA of pigment-producing cells called melanocytes lead to certain melanomas, including superficial spreading melanoma. Researchers are also examining how gene mutations like BRAF contribute to SSM.

Several factors increase the risk of developing superficial spreading melanoma, including:

• Exposure to UV rays: Sunlight and tanning beds both expose people to ultraviolet rays that may increase the risk of skin cancer, including melanoma skin cancer.
• Fair skin: Light skin that burns easily and skin prone to freckles are risk factors for melanoma.
• Moles: Having many moles (50 or more), or having atypical moles with an irregular shape and/or color, may pose a higher risk.
• Middle age: SSM occurs most often in people ages 30 to 50.
• Race: Melanoma may affect anyone, but people with lighter skin are much more predisposed.
• Family history: If someone in the family has had melanoma, especially a close relative such as a parent or sibling, the risk of developing melanoma is higher. In some cases, this is due to specific gene mutations that have been passed between family members, but often it’s due to having shared risk factors, such as light skin.
• Prior skin cancer: A previous diagnosis, even if it was for basal cell or squamous cell skin cancer, raises the risk of developing melanoma.

Having blue or green eyes, red or blond hair and signs of sun damage are less typical risk factors.

Early diagnosis is crucial in effectively treating superficial spreading melanoma and generally involves the following steps:

Clinical examination, or thoroughly investigating the skin to look for characteristics of SMM

Dermoscopy, a specialized technique performed by a board-certified dermatologist involving a handheld tool that magnifies and brightens the skin

Skin biopsy, or surgically removing suspicious skin tissue for lab analysis to determine whether cancer cells are present

Histopathology, which examines tissues under a microscope to check for signs of disease, confirm SSM or identify mutated genes causing SSM

If superficial spreading melanoma is suspected, doctors usually perform an excision biopsy to cut out the whole tumor for inspection.

Sometimes, doctors perform additional imaging tests — X-rays, MRIs, ultrasounds, CT scans or PET scans — to see whether the melanoma has spread. They’ll also measure the Breslow thickness, or how deep vertically the melanoma has penetrated the skin and may perform a biopsy of nearby lymph nodes if the melanoma has become invasive.

Staging is a key step in accurately diagnosing any form of melanoma. This process informs doctors how much cancer is in the body and whether it has spread to other areas.

Like other melanoma types, staging for superficial spreading melanoma is based on the American Joint Committee on Cancer (AJCC) TNM system, which assigns stages based on three factors:

• Tumor thickness and ulceration (T)
• Spread to nearby lymph nodes (N)
• Metastasis to other parts of the body (M)

Numbers or letters following T, N and M present further details about each factor. In general, lower numbers mean less cancer spread, higher numbers mean more advanced cancer and earlier letters, like A, mean a lower stage.

To assign an overall stage, the complete T, N and M categories information is combined in a process called stage grouping.

Learn more about the melanoma stages

How Fast Does Superficial Spreading Melanoma Grow?

Superficial spreading melanoma can appear as a flat or raised patch of discolored skin that can resemble a mole, freckle, or liver spot. These spots tend to grow over time.

When caught early, superficial spreading melanoma responds well to treatment.

The primary treatment for most forms of melanoma, including superficial spreading melanoma, is surgery. Physicians may also remove affected lymph nodes.

In cases where melanomas are thin, like SSM, surgery can be curative.

Advanced melanoma may require additional treatments such as chemotherapy, targeted therapy or immunotherapy — all systemic drug therapies — or radiation therapy.

When it comes to superficial spreading melanoma, it’s important to seek experts with experience in treating the disease. The patient’s team of multidisciplinary experts may include:

• A dermatologist, who treats diseases of the skin
• Mohs surgeons, who are specially-trained surgeons who act as the pathologist and surgeon and can provide real-time analysis of the margins
• A surgical oncologist, who uses surgical techniques to remove cancer
• A medical oncologist, who treats cancer with drugs such as chemotherapy, immunotherapy or targeted therapy
• A radiation oncologist, who uses high-energy beams of radiation to destroy cancerous tissue
• A pathologist, who examines tissue samples for diagnostic purposes to help determine a treatment plan
• A radiologist, who utilizes imaging tools and interventional techniques to diagnose and treat cancer
• Supportive care providers, who focus on cancer- and treatment-related side effects and symptom management

When discussing survival rates, it’s important to consider the size, thickness, location and stage of superficial spreading melanoma as well as the patient’s overall health.

The percentage of people still alive five years after a cancer diagnosis, compared to people without that cancer type, is called the five-year relative survival rate. According to a 2016 study in BMC Cancer, the five-year relative survival rates for superficial spreading melanoma are:

• 99.2%, for local SSM (confined to the original site)
• 71.5%, for regional SSM (spread to nearby tissues or lymph nodes)
• 33.8%, for distant SSM (spread to distant parts of the body)

In a 2021 study that looked at nearly 100,000 people with SMM, the five-year relative survival rate was 87.3% for people diagnosed between 2004 and 2009. The rate rose to 89.7% for people diagnosed between 2010 and 2015.

Patients should talk to the care team to get a personalized SSM prognosis based on such factors as their cancer stage, their overall health and their treatment goals.