Breast cancer staging

, Assistant Editor(s)-In-Chief: Jack Khouri

Overview
Breast cancer is staged according to the TNM system, updated in the American Joint Committee on Cancer (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.

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+). 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.