Breast Cancer Diagnosis

A cancer’s stage is used to describe the extent of the cancer in the patient’s body. Doctors use the stage to plan treatment and make a prognosis.

(source: National Cancer Institute)

There are two staging systems used in the United States for breast cancer. Several factors are used in these systems, including:

• The cancer’s molecular subtype.
• The cancer’s grade. Grading describes a cancer based on how abnormal the cancer cells and tissue look under a microscope and how quickly the cancer cells are likely to grow and spread. Low-grade cancer cells look more like normal cells and tend to grow and spread more slowly than high-grade cancer cells.
• The cancer’s TNM status. The TNM system describes the disease by:
  • Tumor (T): The size and location of the tumor.
  • Lymph node (N): The size and location of lymph nodes where cancer has spread.
  • Metastasis (M): The spread of cancer to other parts of the body.

The stages used in the U.S. are:

• Clinical Prognostic Stage: This is used first to assign a stage for all patients based on health history, physical exam, imaging tests (if done), and biopsies. The Clinical Prognostic Stage is described by the TNM system, tumor grade and biomarker status (ER, PR, HER2). In clinical staging, mammography or ultrasound is used to check the lymph nodes for signs of cancer.
• Pathological Prognostic Stage: This system is used for patients who have surgery as their first treatment. The Pathological Prognostic Stage is based on all clinical information, biomarker status, and laboratory test results from breast tissue and lymph nodes removed during surgery.

TNM System

The TNM system plays a key part in breast cancer staging. It describes the cancer in the by tumor, node and metastasis.

Tumor (T). The size and location of the tumor.

• Primary tumor cannot be assessed.
• T0: No sign of a primary tumor in the breast.
• Tis: Carcinoma in situ. There are 2 types of breast carcinoma in situ:
  • Tis (DCIS): DCIS is a condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive breast cancer that is able to spread to other tissues. At this time, there is no way to know which lesions can become invasive.
  • Tis (Paget disease): Paget disease of the nipple is a condition in which abnormal cells are found in the skin cells of the nipple and may spread to the areola. It is not staged according to the TNM system. If Paget disease AND an invasive breast cancer are present, the TNM system is used to stage the invasive breast cancer.
• T1: The tumor is 20 millimeters or smaller. There are 4 subtypes of a T1 tumor depending on the size of the tumor:
  • T1mi: the tumor is 1 millimeter or smaller.
  • T1a: the tumor is larger than 1 millimeter but not larger than 5 millimeters.
  • T1b: the tumor is larger than 5 millimeters but not larger than 10 millimeters.
  • T1c: the tumor is larger than 10 millimeters but not larger than 20 millimeters.
• T2: The tumor is larger than 20 millimeters but not larger than 50 millimeters.
• T3: The tumor is larger than 50 millimeters.
• T4: The tumor is described as one of the following:
  • T4a: the tumor has grown into the chest wall.
  • T4b: the tumor has grown into the skin—an ulcer has formed on the surface of the skin on the breast, small tumor nodules have formed in the same breast as the primary tumor, and/or there is swelling of the skin on the breast.
  • T4c: the tumor has grown into the chest wall and the skin.
  • T4d: inflammatory breast cancer—one-third or more of the skin on the breast is red and swollen (called peau d’orange).

Lymph Node (N). The size and location of lymph nodes where cancer has spread.

When the lymph nodes are removed by surgery and studied under a microscope by a pathologist, pathologic staging is used to describe the lymph nodes. The pathologic staging of lymph nodes is described below.

• NX: The lymph nodes cannot be assessed.
• N0: No sign of cancer in the lymph nodes, or tiny clusters of cancer cells not larger than 0.2 millimeters in the lymph nodes.
• N1: Cancer is described as one of the following:
  • N1mi: cancer has spread to the axillary (armpit area) lymph nodes and is larger than 0.2 millimeters but not larger than 2 millimeters.
  • N1a: cancer has spread to 1 to 3 axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters.
  • N1b: cancer has spread to lymph nodes near the breastbone on the same side of the body as the primary tumor, and the cancer is larger than 0.2 millimeters and is found by sentinel lymph node biopsy. Cancer is not found in the axillary lymph nodes.
  • N1c: cancer has spread to 1 to 3 axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters. Cancer is also found by sentinel lymph node biopsy in the lymph nodes near the breastbone on the same side of the body as the primary tumor.
• N2: Cancer is described as one of the following:
  • N2a: cancer has spread to 4 to 9 axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters.
  • N2b: cancer has spread to lymph nodes near the breastbone and the cancer is found by imaging tests. Cancer is not found in the axillary lymph nodes by sentinel lymph node biopsy or lymph node dissection.
• N3: Cancer is described as one of the following:
  • N3a: cancer has spread to 10 or more axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters, or cancer has spread to lymph nodes below the collarbone.
  • N3b: cancer has spread to 1 to 9 axillary lymph nodes and the cancer in at least one of the lymph nodes is larger than 2 millimeters. Cancer has also spread to lymph nodes near the breastbone and the cancer is found by imaging tests;
    or
    
  • cancer has spread to 4 to 9 axillary lymph nodes and cancer in at least one of the lymph nodes is larger than 2 millimeters. Cancer has also spread to lymph nodes near the breastbone on the same side of the body as the primary tumor, and the cancer is larger than 0.2 millimeters and is found by sentinel lymph node biopsy.
  • N3c: cancer has spread to lymph nodes above the collarbone on the same side of the body as the primary tumor.

When the lymph nodes are checked using mammography or ultrasound, it is called clinical staging. The clinical staging of lymph nodes is not described here.

Metastasis (M). The spread of cancer to other parts of the body.

• M0: There is no sign that cancer has spread to other parts of the body.
• M1: Cancer has spread to other parts of the body, most often the bones, lungs, liver, or brain. If cancer has spread to distant lymph nodes, the cancer in the lymph nodes is larger than 0.2 millimeters. The cancer is called metastatic breast cancer.