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Please help us save lives through vital breast cancer research

Breast cancer is classified by stages of development. The classification allows a better understanding of prognosis and treatment.

Early (zero) stage of breast cancer is considered as a state in which the atypical cells are localized in the breast tissue and there are no signs that they have spread to the lymph nodes.

Stage 1 of breast cancer: tumor size less than two centimeters (approximately an inch) and has not spread to surrounding lymph nodes or outside the breast.

Stage 2 breast cancer is divided into two groups: the size of the tumor and whether or not it has spread to the lymph nodes:

Stages of breast cancer

2A: tumor less than 2 cm in cross section with the spread to the lymph node, or tumor from 2 to 5 cm without the spread to auxiliary lymph nodes.

2B: tumor more than 5 cm in cross section (the result of auxiliary lymph nodes research is negative for cancer cells) or tumor from 2 to 5 cm in diameter with the involvement of auxiliary lymph nodes. Late (metastatic) stages of breast cancer occur when cancer cells spread to the lymph nodes and other tissues.

Stage 3 breast cancer is also divided in to two categories:

3A: tumor measures more than 5 cm with spread to auxiliary lymph nodes (local spread of breast cancer) or tumor of any size with metastases in auxiliary lymph nodes, which are weaved to each other or with the adjacent tissues.

3B: tumor (any size) with metastases into the skin, chest wall or internal lymph nodes of mammary gland (found below the breast inside of chest).

Stage 4 is defined by the spread of the cancer to other organs or tissues, such as the liver, lungs, brain, skeletal system, or lymph nodes near the collarbone.

Updated 05/23/2014

The Breast Cancer Society of Canada is a tax-exempt and registered charity (charitable registration number 137969861R0001).