Stage I includes: IA: (T1a, N0, M0); IB: (T1b, N0, M0); (T2a, N0, M0). T1a: Cutaneous melanoma with a tumor measuring 1.0 mm or less in thickness, without ulceration and mitosis less than 1/mm2. T1b: Cutaneous melanoma with a tumor measuring 1.0 mm or less in thickness, with ulceration or mitoses equal to or more than 1/mm2. T2a: Cutaneous melanoma with a tumor measuring 1.01-2.0 mm in thickness, without ulceration. N0: No regional lymph node metastases. M0: No detectable evidence of distant metastases. (from AJCC 7th Ed.) [from NCI]