Superficial spreading melanoma stage III Basic Information

Understanding Superficial Spreading Melanoma Stage III

Superficial spreading melanoma is the most frequent type of melanoma, accounting for approximately two-thirds of all melanoma cases diagnosed in places like Australia and New Zealand. This form of skin cancer develops from melanocytes, which are specialized cells in the outer layer of skin responsible for producing melanin, the pigment that gives skin its color.12

When doctors diagnose superficial spreading melanoma at stage III, it means the cancer has spread beyond the original tumor site. Stage III melanoma, also called regional melanoma, indicates that cancer cells have metastasized to nearby lymph nodes, lymph vessels, or surrounding skin areas. Lymph nodes are small, bean-shaped structures that form part of the lymphatic system, a network throughout the body that helps eliminate waste and supports the immune system by transporting infection-fighting white blood cells.11

Stage III melanoma is divided into four subgroups—IIIA, IIIB, IIIC, and IIID—based on several factors including whether the primary tumor shows ulceration (broken skin when viewed under a microscope), the thickness of the original tumor, and how extensively the cancer has spread to lymph nodes or nearby skin. For example, Stage IIIA melanoma might involve a tumor up to 1.0 millimeter thick with spread to up to three nearby lymph nodes detected through sentinel lymph node biopsy, but without distant spread to other organs.11

How Common Is This Condition

Superficial spreading melanoma is notably more common among people with white skin. According to data from New Zealand, at least 40% of the 2,256 invasive melanomas diagnosed in 2008 were classified as superficial spreading melanoma. While this cancer type is most frequent in very fair skin types that burn easily, it can also develop in people who tan relatively easily. It remains rare in individuals with brown or black skin.33

This type of melanoma affects males and females equally. The majority of cases occur in adults, with only about 15% of melanomas appearing before age 40, and diagnosis before age 20 is uncommon. The location where superficial spreading melanoma appears differs between sexes: in males, approximately 40% of cases occur on the trunk (chest, back, abdomen), while in females, about 40% develop on the legs—areas that typically receive intermittent but intense sun exposure.33

Multiple studies have estimated that the incidence rate of stage III melanoma specifically falls somewhere between 1.22 and 1.47 cases per 100,000 people annually. This represents a more advanced form of the disease where early intervention opportunities have passed, making awareness of risk factors and symptoms particularly important.4

What Causes Superficial Spreading Melanoma

Superficial spreading melanoma develops when melanocytes in the skin undergo malignant changes and begin growing abnormally. Most cases arise in previously normal-appearing skin, though approximately 25% develop within an existing mole. These pre-existing moles might be normal common moles, atypical or dysplastic moles, or congenital moles present from birth.33

The precise trigger that causes melanocytes to become malignant remains not fully understood by researchers. However, scientists have identified specific gene mutations, such as BRAFV600E, in many superficial spreading melanomas. These genetic changes may evolve as the disease progresses. The development of cancer involves damage to the cell's DNA, which alters particular genes that control how cells grow and divide. When DNA damage occurs and these altered cells begin reproducing uncontrollably, cancer can develop.35

Ultraviolet radiation plays a central role in melanoma development. Exposure to UV rays from natural sunlight or artificial sources like tanning beds damages the skin's DNA. This damage can result in a degree of immune tolerance, allowing abnormal cells to grow without the body's defense system stopping them. Statistics indicate that approximately 86% of melanomas are caused by solar ultraviolet rays, making sun exposure the most significant environmental factor.35

Who Is at Higher Risk

Several factors significantly increase the likelihood of developing superficial spreading melanoma. Having more than five atypical moles—sometimes called funny-looking moles or moles that appear abnormal under microscopic examination—represents one of the strongest individual risk factors. People with a strong family history of melanoma, particularly those with two or more first-degree relatives (parents, siblings, children) affected by the disease, face elevated risk.33

Skin characteristics heavily influence melanoma risk. Fair skin that burns easily rather than tanning presents higher vulnerability. Additional moderate risk factors include having blue or green eyes, red or blonde hair, working indoors but recreating outdoors, and visible signs of sun damage on the skin. A history of blistering sunburns, especially during childhood and adolescence, substantially increases lifetime risk.33

People who use tanning beds expose themselves to concentrated UV radiation, significantly raising their melanoma risk. Both natural sun exposure and artificial UV sources contribute to DNA damage in skin cells. Individuals with weakened immune systems, whether from medical conditions or medications that suppress immunity, also face increased susceptibility to developing melanoma.56

Recognizing the Symptoms

Superficial spreading melanoma typically presents as a slowly growing or changing flat patch of discolored skin. In its early stages, it may closely resemble a normal mole, freckle, or age spot, making early detection challenging. The lesion becomes more distinctive over time, potentially growing over months, years, or even decades before recognition as concerning.33

Healthcare professionals and patients use the ABCDE memory tool to identify suspicious features that may indicate melanoma. A stands for Asymmetry—one half of the lesion doesn't match the other half. B represents Border irregularity—the edges appear jagged, uneven, or poorly defined rather than smooth and regular. C indicates Color variation—the lesion displays multiple colors including shades of brown, black, blue, gray, pink, red, or white, or areas that look like normal skin. D means Diameter—the spot measures greater than 6 millimeters across, roughly the size of a pencil eraser tip. E signifies Evolving—the lesion is new or changing in size, shape, or color over time.35

Superficial spreading melanoma may appear flat or slightly elevated from the surrounding skin. When diagnosed, the average size is approximately 20 millimeters (three-quarters of an inch) across. Some melanomas don't fit the ABCDE pattern perfectly, so any unusual skin changes, sores that won't heal, or moles that look different from others—sometimes called the "ugly duckling" sign—warrant medical evaluation.35

In stage III disease, patients may not notice any symptoms related to lymph node involvement, as the cancer spread might only be detectable through medical testing. However, some individuals may feel swollen or enlarged lymph nodes near the original melanoma site, appearing as lumps under the skin in areas like the neck, under the arms, or groin.22

Prevention Strategies

Preventing superficial spreading melanoma centers primarily on protecting skin from ultraviolet radiation. Limiting sun exposure, especially during peak intensity hours typically between 10 a.m. and 4 p.m., reduces UV damage accumulation over a lifetime. When outdoors, seeking shade, wearing protective clothing including long sleeves and wide-brimmed hats, and applying broad-spectrum sunscreen with adequate sun protection factor significantly decrease risk.5

Avoiding tanning beds and artificial UV sources entirely eliminates a controllable risk factor. These devices deliver concentrated UV radiation that damages skin cells similarly to natural sunlight. Statistics show that tanning bed use increases melanoma risk substantially, making their avoidance an important preventive measure.5

Regular skin self-examinations help identify new or changing lesions early, when treatment is most effective. Knowing your skin's normal appearance and checking monthly for new moles or changes in existing ones enables prompt medical consultation when suspicious features appear. People at higher risk—those with fair skin, multiple moles, family history of melanoma, or previous skin cancer—should have professional skin examinations by a dermatologist at intervals recommended by their healthcare provider.5

For individuals with known risk factors, genetic counseling and testing may provide valuable information about inherited susceptibility. Understanding personal risk levels allows for more vigilant monitoring and preventive strategies tailored to individual circumstances.6

How the Disease Affects the Body

In the earliest phases, superficial spreading melanoma grows horizontally within the epidermis, the outermost layer of skin. This is called the radial growth phase or in situ phase, where malignant cells remain confined to the epidermis for a prolonged period, potentially months to decades. During this stage, the melanoma presents as a slowly enlarging flat area of discolored skin as abnormal melanocytes multiply along the basal layer of the epidermis.33

An unknown proportion of superficial spreading melanomas eventually become invasive. This critical transition occurs when melanoma cells cross the basement membrane—the boundary separating the epidermis from the deeper dermis layer. Once malignant melanocytes enter the dermis, they gain access to blood vessels and lymphatic channels, creating pathways for potential spread to other body parts. Sometimes a rapidly growing nodular melanoma arises within the superficial spreading melanoma, proliferating deeply into the skin layers.33

By stage III, the pathophysiology has advanced beyond the original tumor site. Cancer cells have traveled through lymphatic vessels to reach regional lymph nodes. The lymphatic system, designed to filter harmful substances and support immune function, ironically becomes a highway for cancer spread. When melanoma cells lodge in lymph nodes, they may multiply there, potentially causing the nodes to swell. The presence of cancer in lymph nodes represents a significant change in disease behavior, indicating greater likelihood of further spread if not treated effectively.12

The body's immune system plays a complex role in melanoma development and progression. UV radiation damage results in a degree of immune tolerance, where the immune system fails to recognize and eliminate abnormal cells as it normally would. This compromised surveillance allows melanoma cells to grow unchecked. However, the immune system remains important in controlling the disease, which is why some newer treatments work by boosting immune responses against melanoma cells.3