Melanoma is a serious form of skin cancer that develops from melanocytes, the cells responsible for producing skin pigment. While less common than other skin cancers, melanoma is more likely to spread to other parts of the body, making early detection and understanding its progression particularly important.
Understanding Melanoma’s Origin
Melanoma originates in melanocytes, specialized cells located in the top layer of the skin, the epidermis, that produce melanin. Melanin is the pigment that gives skin, hair, and eyes their color and offers some protection against ultraviolet (UV) radiation.
Damage to the DNA within these melanocytes, often induced by UV radiation from sunlight or tanning beds, can disrupt their normal growth control. This DNA damage can lead to uncontrolled proliferation of these cells, forming a tumor. Melanoma can develop in an existing mole, especially an atypical mole, or appear as a new, unusual pigmented lesion on previously clear skin.
How Melanoma Progresses and Spreads
Melanoma typically progresses through distinct growth phases, beginning with a horizontal spread. The initial stage is the radial growth phase, where the melanoma cells grow outward within the epidermis. During this phase, the cancer cells generally remain confined to the epidermis and do not spread to distant sites.
Following the radial growth, some melanomas enter a vertical growth phase, where cancer cells invade deeper into the dermis. This deeper invasion is a significant step in the tumor’s progression and increases the likelihood of metastasis, the spread of cancer cells beyond the primary tumor. Nodular melanoma, a specific type, often skips the radial growth phase and presents directly with vertical growth.
Once melanoma cells invade deeper, they can access blood vessels and lymphatic channels. This allows them to travel from the primary tumor to regional lymph nodes. From the lymph nodes, melanoma cells can then spread through the bloodstream or lymphatic system to distant organs, such as the lungs, liver, or brain. The depth of invasion, often measured as Breslow thickness, is a significant indicator of prognosis, with thicker tumors having a greater chance of spreading.
Recognizing Melanoma Growth
Observing changes in existing moles or the appearance of new, unusual spots is an important step in early melanoma detection. The “ABCDEs” of melanoma guide identifying concerning skin lesions.
- Asymmetry: One half of the mole does not match the other.
- Border irregularity: Edges are uneven, ragged, notched, or blurred.
- Color variation: Multiple shades of brown, black, or tan, sometimes including white, gray, red, pink, or blue.
- Diameter: Moles are typically larger than 6 millimeters, though melanomas can be smaller, especially in their early stages.
- Evolving: Any changes in a mole’s size, shape, color, or elevation. New symptoms like itching, tenderness, or bleeding within a mole also require prompt attention.
Factors Influencing Melanoma Development
Exposure to ultraviolet (UV) radiation is a primary factor in melanoma development. Both sun exposure, particularly intense, intermittent exposure leading to sunburns, and artificial UV sources like tanning beds, can damage DNA in skin cells and contribute to melanoma formation. Frequent severe sunburns, especially during childhood, can increase the risk.
Genetic predisposition also plays a role, with about one in ten melanoma cases having a family history of the disease. Individuals with fair skin, light hair, light eye color, and those who sunburn easily have a higher susceptibility due to less protective melanin. The presence of many moles, or atypical moles, further increases an individual’s risk.
A weakened immune system, whether due to medical conditions or immunosuppressive medications, can also elevate the risk of developing melanoma.