Stage IA includes: T1a, Any N, M0. T1a: Tumor diagnosed only by microscopy. Stromal invasion with a maximum depth of 5.0 mm measured from the base of the epithelium and a horizontal spread of 7.0 mm or less. Vascular space involvement, venous or lymphatic, does not affect classification. M0: No distant metastasis. (AJCC 8th Ed.) [from NCI]