Stage 1 melanoma is defined as a melanoma that is up to 2mm thick. There are two subclasses of Stage I: 1A (less than 0.8mm); 1B ( 0.8 -1mm or any melanoma less than 1mm with ulceration and melanoma 1-2mm without ulceration). There is no evidence the cancer has spread to lymph nodes or distant sites (metastasis).