Stages of Cancer

Staging of cancer is done to describe the extent of cancer, which includes size of the primary tumour, its spread to the regional lymph nodes and its status of metastasis. The staging helps in assessing the treatment & prognosis of cancer. There are different staging systems, for example, Dukes & Astler Coller staging system (used to stage a colorectal cancer) and Clark's level staging system (used in malignant melanoma). The most common and globally accepted staging system is 'TNM' classification. This staging system describes the size (or number) of the primary tumour (T); involvement of the regional lymph nodes (N); and the status of metastasis (M). The letter (T) is followed by: ‘x’ if the primary tumour is not assessed clinically; ‘0’ if there is no evidence of primary tumour; ‘IS’ if the tumour is in situ; or it is followed by the number 1, 2, 3 or 4, which denotes the size of tumour. The greater the number, the larger the size of the tumour. The letter (N) is followed by: ‘x’ if the involvement of regional lymph nodes is not assessed clinically; ‘0’ if the regional lymph nodes are not involved; or it is followed by the number 1, 2, 3 or 4, which denotes the extent of involvement of regional lymph nodes. The letter (M) is followed by: ‘x’ if the metastasis is not assessed clinically; ‘0’ if there is no evidence of metastasis; or ‘1’ if the cancer has metastasised. These numbers are usually translated for convenience of the patient, as Stage I, Stage II, Stage III, etc.