NCIt definition : Stage IB includes: T2a, N0, M0. T2a: Tumor measuring more than 1.0 and equal to or
less than 2.0 mm in thickness. Ulceration status: Without ulceration. N0: No regional
lymph node metastasis detected. Presence of in-transit, satellite, and/or microsatellite
metastases: No. M0: No evidence of distant metastasis. LDH level is not applicable.
(AJCC 8th ed.);