Once the type of melanoma has been established, the next step is to classify the disease as to its degree of severity.
Classifications for melanomas are called stages. The stage depends on the thickness, depth of penetration, and the degree to which the melanoma has spread. The staging is used to determine treatment.
Early melanomas (Stages 0 and I) are localized; Stage 0 tumors are in situ, meaning they are noninvasive and have not penetrated below the outer layer of the skin (the epidermis). Stage I tumors have invaded below the epidermis into the skin’s next layer (the dermis) but are small and have no other traits such as ulceration that put them at high risk of spreading (metastasizing) to nearby lymph nodes or beyond.
Stage II tumors, though localized, are larger (generally 1 mm. thick or larger) and/or may have other traits such as ulceration that put them at high risk of spreading to the nearby lymph nodes or beyond. They are considered intermediate or “high-risk” melanomas. More advanced melanomas (Stages III and IV) have metastasized to other parts of the body. There are also subdivisions within stages.