Smoking is one of the main reasons of developing cancer of lungs. But lung cancer has also been detected in patients who never smoked or were exposed to secondary smoke.
Smoking damages the cell lining around lungs and with repeated exposure causes cells to act abnormally which ultimately develops into cancer.
The most common system used for staging lung cancer is the TNM system.
T stands for Tumour. It is used to describe the size of the tumour. It also helps to determine whether tumour has grown into other parts of the organ or tissues around the organ. It is represented by a range of 1 to 4. The higher the number means the larger the tumour.
N stands for Lymph Nodes. It helps determine if the cancer has spread to the lymph nodes around the organ. NX means the impact on lymph nodes cannot be determined. N0 means cancer hasn’t spread to nearby lymph nodes while N1, N2 and N3 means cancer has spread to lymph nodes. N1 to N3 also shows the range that how many lymph nodes are affected.
M stands for Metastasis. It is used to determine if the cancer has spread to other parts of body through blood or lymphatic system. MX means the metastasis cannot be determined; M0 means cancer has not spread to other body parts while M1 indicates that it has spread to other body parts.
Sometimes lowercase letters like a, b and c is used to divide the tumour, lymph nodes and metastasis into sub categories. Also lowercase “is” is used to denote carcinoma in situ. For e.g. Tis