Breast cancer is staged with the typical I, II, III and IV descriptors, according to the TNM staging classification. In addition, the tumor is given a histologic grade of I, II or III.

Grade I describes a well differentiated cancer and a favorable prognosis, whereas grade III is an undifferentiated cancer and a poor prognosis. Both stage and grade are critical in assessing for the risk of recurrence.

Stages of Breast Cancer

The stage I through IV definitions for breast cancer are listed below. Note that stages II and III contain subtypes, which may be important when considering treatment options. With current screening recommendations, two-thirds of patients are diagnosed with stage I or II. Because breast cancer can be a slow-growing tumor, the listed five-year survival rates drop by about 10 to 20% after ten years of follow-up.

• Stage I: Small tumor localized to one breast. More than 95% of stage I patients will survive 5 years.
• Stage II: Tumor is larger and/or has spread to axillary lymph nodes – 85% survive 5 years.
• IIA: Tumor less than 2 cm and axillary lymph nodes are POSITIVE or tumor 2 to 5 cm and axillary lymph nodes are NEGATIVE.
• IIB: Tumor 2 to 5 cm and axillary lymph nodes are positive or tumor greater than 5 cm and axillary lymph nodes are negative.
• Stage III: Tumor invades chest wall or more lymph nodes involved – 35% survive 5 years.
• IIIA: Tumor greater than 5 cm and axillary lymph nodes are positive or tumor of any size and axillary lymph nodes are fixed and/or matted together.
• IIIB: Tumor invades the chest wall or has ulcerated (includes inflammatory subtype).
• IIIC: Tumor of any size with additional lymph node involvement, such as internal mammary, infraclavicular or supraclavicular nodes.
• Stage IV: Tumor has spread to distant sites (metastatic) – 25% survive 5 years. Distant metastases present, often the liver, lung, bone, or brain