The TNM classification for lung cancer is a tool used to assess the progression of lung cancer based on three main components: the size and extent of the primary tumor (T), the involvement of nearby lymph nodes (N), and the presence of distant metastasis (M). By analyzing these factors, the calculator categorizes the cancer into distinct stages, providing a standardized way to understand the severity and spread of the disease. Here's how it works:

- **Tumor Classification (T):** 
  - Tx: The primary tumor cannot be assessed.
  - Tis: Carcinoma in situ, with the earliest form of tumor that has not spread.
  - T1mi, T1a, T1b, T1c: Tumors of increasing size, still relatively small (up to 3 cm).
  - T2a, T2b: Larger tumors (up to 5 cm) that may invade certain parts of the lung.
  - T3, T4: Even larger tumors (up to 7 cm) or tumors invading major structures or showing additional nodules.

- **Lymph Node Classification (N):**
  - Nx: Lymph nodes cannot be assessed.
  - N0: No lymph node metastasis.
  - N1: Metastasis in nearby or regional nodes.
  - N2: Metastasis in specific mediastinal nodes.
  - N3: Metastasis in more distant or contralateral nodes.

- **Distant Metastasis (M):**
  - M0: No distant metastasis.
  - M1a, M1b: Presence of metastasis in the same or a single other organ.
  - M1c: Multiple metastases in multiple organs.

By inputting these three parameters, the calculator determines the overall stage of lung cancer through a series of predefined conditions:

- If the cancer is classified as "Tis" with no node involvement (N0) and no metastasis (M0), the stage is classified as Stage 0, indicating a very early stage.
- Early stages such as Stage IA, IB, and IIA are characterized by small tumors with limited node involvement and no metastasis.
- As the tumor size increases or node involvement becomes significant, the stage progresses to IIB, IIIA, IIIB, and eventually IIIC, each indicating more advanced local and nodal disease.
- The presence of distant metastasis (M1a, M1b, or M1c) automatically pushes the classification to Stage IV, with IVB representing the most advanced and widespread disease due to multiple extrathoracic metastases.

Through this structured interpretation, medical professionals can understand the extent of lung cancer and guide treatment decisions based on the specific stage identified.

The TNM classification for lung cancer is a staging system developed by the American Joint Committee on Cancer (AJCC). It is designed for the stratification of patients with lung cancer based on the extent of the disease, which is crucial for treatment planning and prognosis estimation.

The TNM classification system comprises three primary components: T (tumor), N (nodes), and M (metastasis). The T component describes the size of the primary tumor and whether it has invaded nearby structures. The N component indicates whether the cancer has spread to nearby (regional) lymph nodes. The M component reveals whether the cancer has metastasized to distant parts of the body. Each component is assigned a numerical value based on the extent of the disease, with higher numbers indicating more advanced disease.

The final stage of the disease, ranging from stage I (early stage) to stage IV (advanced stage), is determined by combining the T, N, and M values. This comprehensive staging system allows clinicians to accurately assess the extent of the disease, guide treatment decisions, and predict patient outcomes.