Understanding Breast Cancer Stages and Staging

Understanding breast cancer staging is a critical step of the diagnostic process and helps with prognosis and proper treatment.

Breast Cancer Staging Using the TNM Staging System

TNM stands for Tumor, Nodes, Metastases, a 1992 (updated in 2002) cancer staging classification of the American Joint Committee on Cancer and the International Union Against Cancer. This system may be applied to various organs and helps establish a basis for breast cancer prognosis.

TX: tumor cannot be measured/found
T0: no evidence of tumor
Tis: tumor is in situ
T1-T4: the higher the number the larger or more invasive the tumor
NX: nearby lymph nodes cannot be assessed
N0: nearby lymph nodes are not affected
N1-N3: the higher the number to more involved the lymph nodes are
MX: metastasis cannot be measured/found
M0: no known metastasis
M1: metastasis is present.

The values ascribed to T, N and M are used to determine the stage of the cancer.

Stages of Breast Cancer

Stage 0 describes the earliest of breast cancer stages. Typically, breast cancer begins as a carcinoma in situ meaning that it is localized in a duct or lobule (TisN0M0). Growth rate varies but the "wild" cells remain together. Stage 0 cancer is non-invasive. The prognosis for individuals with a carcinoma in situ is that all will be alive after five years, provided that the entire tumor is successfully removed.

If the carcinoma in situ is not identified and removed, it is liable to continue growing to Stage I.

Stage I cancer is invasive but is confined to the breast and is less than two centimeters (4/5 inch) in diameter (T1N0M0). Approximately 98 percent of Stage I patients are alive five years after diagnosis and treatment.

Stage II is characterized by a combination of tumor size and the distance the disease has spread. Stage II is divided into two stages: IIA and IIB

In Stage IIA either no primary tumor can be found, but the disease has spread to lymph nodes in the armpit (T0N1M0), the tumor measures less than 2 cm (4/5 in) in diameter and the disease has not spread (T1N0M0), or the tumor's diameter is between 2 and 5 cm (4/5 to 2 in) and has not spread to the lymph nodes (T2N0M0). Five-year survival rate for Stage IIA patents is 88 percent.
Stage IIB tumors measure 2 to 5 cm (4/5 to 2 in) in diameter and have spread to nearby lymph nodes (T2N1M0) or the tumor is larger than 5 cm (2 in) and has not spread to the lymph nodes (T3N0M0). Five-year survival rate for Stage IIB patents is 76 percent.

Stage III is divided into three stages: IIIA, IIIB and IIIC.

Stage IIIA development is characterized by a less-than-5 cm (2 in) tumor where the disease has spread to armpit lymph nodes on the same side (T0-2N2M0). Alternatively, the tumor is larger than 5 cm (2 in) and has spread to armpit nodes on the same side (T3N1-2M0). Five-year survival rate for Stage IIIA patents is 56 percent.
At Stage IIIB, the disease has spread to the chest wall, ribs or muscles (T4N0-2M0). The skin is also likely to have been invaded. Lymph nodes on the cancer side may or may not be affected. Five-year survival rate for Stage IIIB patents is 49 percent.
Stage IIIC disease is a tumor of any size that has spread to numerous lymph nodes on the same side as the cancer (T0-4N3M0). (Five-year survival rate for Stage IIIC patients is not yet available.)

Stage IV is well advanced; regardless of the size of the tumor or number of lymph nodes affected the disease has metastasized to bones, lungs, liver, brain or other body organs (T0-4N0-3M1). Stage IV offers the lowest probability for survival of any of the stages. The five-year survival is 16 percent. Once it has spread to internal organs, the prognosis is poor.

Recurrent cancer is cancer that returns following treatment.

At a Glance: Staging Using TNM
Stage	Tumor	Nodes	Metastasis
I	Less than 2 cm (4/5 in)	No involvement	No metastasis
II	2 to 5 cm (4/5 to 2 in)	Nodes on same side of cancer may or may not be involved	No metastasis
III	Greater than 5 cm (2 in)	Nodes on same side as cancer involved	No metastasis
IV	Any size	May or may not be involved	Metastasis

Physicians may apply the concept of breast cancer prognosis to patients with tumors when they are first detected, or even to individuals who demonstrate certain risk factors. The type of tumor and location, for example, help doctors determine the likelihood of success for a specific treatment regimen and, therefore, the likelihood of a tumor recurring.

Once a stage has been determined, the cancer is always referred to as in that stage, even if the disease progresses. Someone diagnosed with Stage IIIA breast cancer will always be a Stage IIIA patient, even if the cancer metastasizes to another organ. The cancer would then be called "Stage IIIA breast cancer with metastasis in the lungs" (or other organ affected).

Resources

American Cancer Society. (revised 2004, September). How is breast cancer staged?

Imaginis Corporation. (updated 2004, September). Staging and survival rates of breast cancer.