Stage I Lung Cancer AJCC v9

**Semantic type:** Neoplastic Process

**Definition:** Stage I includes: IA1: (T1mi, N0, M0); (T1a, N0, M0); IA2: (T1b, N0, M0); IA3: (T1c, N0, M0); IB: (T2a, N0, M0). T1mi: Minimally invasive adenocarcinoma: adenocarcinoma (3 cm or less in greatest dimension) with a predominantly lepidic pattern and 5 mm or less invasion in greatest dimension. T1a: Tumor measuring 1 cm or less in greatest dimension or tumor of any size whose invasive component is limited to the bronchial wall and may extend proximal to the main bronchus, but this is an uncommon superficial spreading tumor. T1b: Tumor measuring more than 1 cm but 2 cm or less in greatest dimension. T1c: Tumor measuring more than 2 cm but 3 cm or less in greatest dimension. T2a: Tumor measuring more than 3 cm but 4 cm or less in greatest dimension or tumor measuring 4 cm or less in greatest dimension with one or more of the following features: invasion of visceral pleura; invasion of an adjacent lobe; involvement of main bronchus (up to but not including the carina) or is associated with atelectasis or obstructive pneumonitis, extending to the hilar regions, involving either part of or the entire lung. N0: No tumor involvement of regional lymph node(s). M0: No distant metastasis. (AJCC 9th ed.)