Breast cancer can be classified in the following stages:

STAGE 0: This is non-invasive DCIS (ductal carcinoma in situ); the cancer stays within the ducts of the breast. Some consider this to be pre-cancer.

STAGE I: This is early invasive breast cancer. The tumour is 2 cm or less and cancer has not spread to lymph nodes.

STAGE II: This is still considered early invasive breast cancer, but the tumour is larger (2 – 5 cm) and/or the cancer has spread to a few nearby lymph nodes.

STAGE III: This is locally advanced breast cancer. The tumour is either larger than 5 cm, or extends to the chest wall or involves the skin of the breast, or has spread to many nearby lymph nodes.

STAGE IV: This is metastatic or advanced breast cancer. The cancer has spread to other parts of the body, such as bone, liver, lungs, or brain.