How Melanoma Spreads
If melanoma grows at the site of the original tumor, it tends to grow in one of two ways:
Radial growth. This means the melanoma spreads horizontally along the top layers of your skin. Most melanomas start growing this way, but some may eventually grow into deeper layers of your skin.
Vertical growth. This means melanoma grows into deeper layers of skin. This kind of growth is more serious and may spread to other parts of the body. Some melanomas grow this way fairly quickly, but most grow along the top layers of skin first for some time.
Melanoma's growth to distant areas of your body is somewhat unpredictable. It tends to spread first to lymph nodes in the area of your original tumor. For example, if the tumor was on your leg, it may spread to lymph nodes in your groin area. But, sometimes, melanoma may spread to distant areas of your body, even if your lymph nodes have not been involved.