Breast Cancer - Staging

Breast cancer is staged according to the TNM system, updated in the AJCC Staging Manual, now on its sixth edition. Prognosis is closely linked to results of staging, and staging is also used to allocate patients to treatments both in clinical trials and clinical practice. The information for staging is as follows:

TX: Primary tumor cannot be assessed. T0: No evidence of tumor. Tis: Carcinoma in situ, no invasion T1: Tumor is 2 cm or less T2: Tumor is more than 2 cm but not more than 5 cm T3: Tumor is more than 5 cm T4: Tumor of any size growing into the chest wall or skin, or inflammatory breast cancer

NX: Nearby lymph nodes cannot be assessed N0: Cancer has not spread to regional lymph nodes. N1: Cancer has spread to 1 to 3 axillary or one internal mammary lymph node N2: Cancer has spread to 4 to 9 axillary lymph nodes or multiple internal mammary lymph nodes N3: One of the following applies:

Cancer has spread to 10 or more axillary lymph nodes, or Cancer has spread to the lymph nodes under the clavicle (collar bone), or Cancer has spread to the lymph nodes above the clavicle, or Cancer involves axillary lymph nodes and has enlarged the internal mammary lymph nodes, or Cancer involves 4 or more axillary lymph nodes, and tiny amounts of cancer are found in internal mammary lymph nodes on sentinel lymph node biopsy.

MX: Presence of distant spread (metastasis) cannot be assessed. M0: No distant spread. M1: Spread to distant organs, not including the supraclavicular lymph node, has occurred

Summary of stages:

Stage 0 - Carcinoma in situ
Stage I - Tumor (T) does not involve axillary lymph nodes (N).
Stage IIA – T 2-5 cm, N negative, or T <2 cm and N positive.
Stage IIB – T > 5 cm, N negative, or T 2-5 cm and N positive (< 4 axillary nodes).
Stage IIIA – T > 5 cm, N positive, or T 2-5 cm with 4 or more axillary nodes
Stage IIIB – T has penetrated chest wall or skin, and may have spread to < 10 axillary N
Stage IIIC – T has > 10 axillary N, 1 or more supraclavicular or infraclavicular N, or internal mammary N.
Stage IV – Distant metastasis (M)
Breast lesions are examined for certain markers, notably sex steroid hormone receptors. About two thirds of postmenopausal breast cancers are estrogen receptor positive (ER+) and progesterone receptor positive (PR+).[83] Receptor status modifies the treatment as, for instance, only ER-positive tumors, not ER-negative tumors, are sensitive to hormonal therapy.

The breast cancer is also usually tested for the presence of human epidermal growth factor receptor 2, a protein also known as HER2, neu or erbB2. HER2 is a cell-surface protein involved in cell development. In normal cells, HER2 controls aspects of cell growth and division. When activated in cancer cells, HER2 accelerates tumor formation. About 20-30% of breast cancers overexpress HER2. Those patients may be candidates for the drug trastuzumab, both in the postsurgical setting (so-called "adjuvant" therapy), and in the metastatic setting.