T1b tumors are less than 0.8 mm thick and are ulcerated or are 0.8 to 1.0 mm thick and can be ulcerated or not.T1a tumors are less than 0.8 mm thick and are not ulcerated.The T1 category includes tumors that are less than 1.0 mm thick. This category is related to your primary melanoma tumor. TNM Categories and Subcategories for Stage III Melanoma Costs of Participating in Clinical Trials.Risks of Participating in Clinical Trials.Ocular Melanoma Prevention & Early Detection.
