NCIt definition : Stage IB includes: T1b, N0, M0. T1b: Tumor measuring more than 2 cm in greatest dimension
or with stromal invasion more than 1 mm. Note: Depth of invasion is measured from
the basement membrane of the deepest adjacent tumor-free rete ridge to the deepest
point of invasion. N0: No regional lymph node metastasis. M0: No distant metastasis.
(AJCC 9th Ed.);