Today the accepted staging for breast cancer is the TNM classification which takes into consideration the tumor itself, the involvement of the lymph nodes and the metastasis to other body parts. The mode of treatment best suited for each patient and the prognosis is closely linked to the stage of the tumor.

STAGE 0: In Situ ("in place") disease in which the cancerous cells are in their original location within normal breast tissue.

STAGE I: Tumor that is less than 2 cm in diameter with no spread beyond the breast.

STAGE II: Tumor that is 2 to 5 cm in size without spread to lymph nodes of axilla or tumor less than 2 cm in size with spread to axillary lymph nodes.

STAGE III: Tumor that is smaller than 5 cm in size with spread to axillary lymph nodes which are attached to each other or to other structures.

STAGE IV: A tumor that is of any size, which spread beyond the region of the breast and chest wall, such as to liver, bone, or lungs

Each tumor is classified histologically into the following:-

• well-differentiated tumors (low grade) - resembles normal tissue.

• poorly differentiated tumors (high grade) - composed of disorganized cells, does not resemble normal tissue

• Moderately differentiated tumors (intermediate grade) – has charecteristics that resemble both of the above.