Superficial Spreading Melanoma: The Most Common Type of Melanoma

Superficial spreading melanoma is the most common form of melanoma, making up approximately 70 percent of all melanoma diagnoses. It develops from melanocytes, the pigment-producing cells in the skin, and initially grows outward across the surface of the skin in what is known as the radial growth phase. This subtype can occur at any age but is most frequently diagnosed in younger and middle-aged adults. It can appear anywhere on the body, though it is most common on the trunk in men and on the legs in women.

This melanoma subtype follows a two-phase growth pattern. During the radial growth phase, the cancerous cells spread horizontally along the epidermis and superficial dermis, which can last for months to several years. During this phase, the melanoma remains relatively thin and is highly treatable with surgical excision alone. If left untreated, however, the melanoma eventually transitions into a vertical growth phase, penetrating deeper into the dermis where it can access blood vessels and lymphatics, significantly increasing the risk of metastasis.!!

Superficial spreading melanoma typically presents as a flat or slightly raised lesion with irregular, notched, or scalloped borders. One of its hallmarks is the presence of multiple colors within a single lesion, including shades of brown, black, tan, pink, red, white, and blue-gray. The surface may appear uneven, with some areas raised and others flat. Over time, the lesion tends to grow larger and may develop areas of regression where the color fades, giving it a patchy or mottled appearance.

The ABCDE rule is a widely used guideline to help identify potential melanomas, and superficial spreading melanoma is the subtype that most classically fits these criteria. A stands for Asymmetry, where one half of the lesion does not match the other. B is for Border irregularity, with edges that are ragged or blurred.

C stands for Color variation, with multiple shades present. D refers to Diameter greater than six millimeters. E is for Evolving, meaning the lesion is changing in size, shape, or color over time.

While anyone can develop superficial spreading melanoma, certain factors increase the risk. Fair-skinned individuals with light hair and light eyes are at higher risk, as are those with a history of blistering sunburns, especially during childhood or adolescence. People with a large number of moles, atypical moles, or a family history of melanoma also face elevated risk. Chronic intermittent sun exposure, such as intense recreational sun exposure followed by periods of little exposure, is considered a stronger risk factor than continuous occupational sun exposure.

The primary treatment for superficial spreading melanoma is wide local excision, where the tumor is surgically removed along with a margin of healthy surrounding tissue. For thin melanomas caught in the radial growth phase, surgery alone is often curative. If the melanoma has progressed to a greater thickness, sentinel lymph node biopsy may be recommended to determine whether the cancer has spread. Advanced-stage disease may require additional treatments including immunotherapy with checkpoint inhibitors, targeted therapy for tumors with specific genetic mutations, or radiation therapy.

The prognosis for superficial spreading melanoma is excellent when caught early. Thin melanomas with a Breslow depth of less than one millimeter have five-year survival rates above 95 percent.!! The extended radial growth phase of this subtype provides a valuable window of opportunity for early detection, making regular skin self-examinations and annual professional skin checks critically important. Skinscanner can assist with ongoing skin monitoring by using AI to analyze moles and skin lesions, helping you identify changes that may warrant a visit to your dermatologist.