It is by the decision of the doctor (oncologist) to determine the staging of a Lung cancer, depending on the types of lung cancer that the person has. The cancer’s stage tells you how vast and how far the cancer cells has spread, it also describes the size of tumor and whether lung cancer cells have spread away from the tissue where it started to grow. Staging may vary on each types of lung cancer due cells grow and behave differently. This is vital because it aids the doctor on deciding which type of treatment is needed and most helpful in the case of the patient to be able to know their current condition. The scans and tests that diagnosed the type of lung cancer give the doctors information about the stages of lung cancer and prognosis. There are times that it is not likely to be sure about the stage of lung cancer until the surgery has been done. There are several ways on how oncologists stage cancer. They are TNM and the number staging system. 
TNM staging system:
In this system oncologists puts into account the following;
- The size and the position of the tumor (T)
- Presence of cancer cells in the lymph nodes (N)
- Presence of cancer metastases to different organs (M)
Doctor’s provide a comprehensive work out with the information regarding the factors to be considered.
Number Staging System:
The number staging system is divided into 4 main groups which are:
Stage 0: (carcinoma in situ) abnormal cells are found in the lining of the lungs, and there is a presence of abnormal cells in the lung tissue itself, but then abnormal cells may become cancerous and proliferate and spread out.
Stage 1: (localized) lung cancer is small in size and basically located on one are of the lungs.
1A: the tumor is found in the lung only, with 3 cm in size
1B: the tumor is more than 3cm, and it is growing, affecting the main airways and bronchi, and the lung’s covering (pleura) causing the significant collapse of the lung.
Stage 2 and 3: (secondary localized) lung cancer is bigger and may have significant growth to the surrounding tissues, and presence of cancer cells on the lymph nodes.
Stage 2A: The tumor has spread to nearby lymph nodes and is 3 cm in size.
Stage 2B: The tumor has spread to nearby lymph nodes and it is more than 3cm in size adffecting the chest wall, the pleura, the muscle under the lungs and the covering of the heart, and a there is a total collapse of the lungs tissue (Atelectasis).
Stage 3A: tumor is in any size. There is a significant spread in the lymph nodes in the middle part of the chest but not including the other lobe of the lung,
Stage 3B: the same lung has 2 or more tumors, there is a significant spread on the other tissues and cancer cells are already visible in the pleural fluid.
Stage 4: (secondary or metastatic cancer) when there is already a presence of cancer cells to different part of the body, such as the brain, liver and the bones.
Doctors based their mode of treatment depending on the stages of lung cancer the person already has, the higher the stage, the more comprehensive the treatment goes and this also comes with low lung cancer prognosis. The lower lung cancer stages, the higher is the person’s survival rate and probability of having full recovery which will entail a high lung cancer prognosis.