Stages and Grades of Breast Cancer

Staging

Once breast cancer has been diagnosed, doctors perform tests to determine the stage of the cancer. Staging is the process of determining the size of the tumor and whether it has spread within the breast or to other parts of the body. Doctors use a cancer’s stage as a key factor in making treatment recommendations and estimating the patient’s chance for recovery.

There are two main systems for determining the stage of breast cancer:

• TNM is an acronym of the words tumor, nodes, and metastasis, and this system describes a cancer in terms of the size of the original tumor, whether any lymph nodes are involved, and whether the cancer has metastasized, or spread from the breast to another part of the body.
• Once TNM is determined, a stage is assigned using overall stage grouping, also known as Roman numeral staging. This system uses the numerals 0, I, II, III and IV to describe the progression of cancer, with 0 being pre-cancerous and IV the most advanced.
• The following terms are used loosely to refer to these stages:
  o Non-invasive cancers are at stage 0.
  o Early stage cancers are at stages 1 and 2, and sometimes 3.
  o Advanced cancers are at stages 3 and 4.
   

TNM Staging

T: Tumor Size: The letter T followed by a number from 0 to 4 describes the tumor’s size and whether it has spread to the skin or chest wall under the breast. Higher T numbers indicate a larger tumor and/or more extensive spread to tissues surrounding the breast.

N: Palpable Nodes: The letter N followed by a number from 0 to 3 indicates whether the cancer has spread to lymph nodes near the breast and, if so, whether the affected nodes are fixed to other structures under the arm.

M: Metastasis: The letter M followed by a 0 or 1 indicates whether or not the cancer has metastasized to other organs, such as the lungs or bones, or to lymph nodes that are not next to the breast, such as those above the collarbone.

Overall Stage Grouping

Stage I: The tumor is smaller than 1 inch, and the cancer has not spread to the lymph nodes under the arm or to other sites beyond the breast.

Stage II: The tumor is 1 inch to 2 inches in size, or the cancer has spread to the lymph nodes under the arm.

Stage III: This is a more advanced cancer, but it is still confined to the breast, surrounding tissues, and lymph nodes.

Stage IV: The breast cancer has spread or metastasized to distant sites such as the lungs, liver, bones, and brain, or to lymph nodes outside of the underarm area.

Breast Cancer Grade

The grade of a tumor refers to how closely the cancer resembles normal breast cells. It is a system used for invasive cancers but not for in situ cancers. In general, a lower grade number indicates a slower-growing cancer that is less likely to spread, while a higher number indicates a faster-growing cancer that is more likely to spread.

Grade 1 (well differentiated): Grade 1 breast cancers have relatively normal-looking cells that do not appear to be growing rapidly and are arranged in small tubules.

Grade 2 (moderately differentiated): These cancers have cells that are somewhat abnormal.

Grade 3 (poorly differentiated): The highest grade, these cancers have cells that look abnormal and tend to grow and spread more aggressively.

Updated 8/18/2009