Melanoma in-situ - the melanoma is present only in the epidermis; a Breslow thickness and Clark's level are not determined for this early stage lesion
Stage I - less than 1 mm thick
Stage II - greater than 1 mm thick or Clark's level IV-V (invasion into reticular dermis or subcutaneous tissue)
Stage III - has spread to local lymph nodes (may or may not have known of a primary lesion) or Clark's level V (invades subcutaneous tissue)
Stage IV - presents with distant metastasis (most commonly liver, lung, and brain)
